Mr Blair says that, if it was right to conduct a military campaign, it was right for Britain to be involved. It was best, in such a case, to be "right alongside" the US. If war is thought to be right, the UK "should be prepared to play our part fully", Mr Blair adds.
Re Mike Leeds: It is also likely that those against in these posts were also against the war back to when you refer... Being a good public speaker does not automatically make what that person says is correct... or even true.Luke, Northampton
Mr Blair is asked about "packages" discussed, in terms of the efforts to be made in the event of military action and how he weighed up the risks to personnel. Mr Blair said he asked the military, who were "up for doing it", if war was to happen.
Mr Blair says military action possibilities were discussed at that Crawford meeting with President Bush in April 2002.
After a break which over-ran the original estimate of about 15 minutes, the evidence is about to start again. Mr Blair is back in his seat.
One of the people watching Mr Blair's performance via video link in another room of the Queen Elizabeth II centre has been escorted out after proclaiming "I can't stomach any more of this", the BBC learns.
This is unreal. "We'll come to that..." Blair has now taken over the role of chairman at his own interrogation.
Blair's not doing a very good job selling the 'its been tough but for the best' viewpoint. He looks nervous and unconvincing.
I still believe this inquiry is largely useless, but it has been interesting, it does almost feel trial-like. Blair largely performing well.
The number of protesters gathered in Westminster has "dwindled somewhat", the BBC's Tom Symonds reports. But more are expected to gather towards the end of today's hearing.
Nice to see some balance in the BBC's coverage. I take it you're not receiving anything but anti-Blair comments so they're the only ones you can publish. And, re MJ Dolan Manchester; if millions disagreed with him then how was he elected for a third term more than two years after the invasion with a 66 seat majority? I think you'll find it's called democracy.Lawrence Kershaw, London
It's amazing what hindsight does to a number of people. While there was an opposition to the war, there seemed a clear majority that backed our forces and decisions to go in to Iraq. I'm quite enjoying Tony showing again how good a public speaker he is.Mike C, Leeds
I thought Iraq was a secular state under Saddam Hussein, so what has he to do with 9/11 and Islamic Fundamentalism?Steven Danesi, London
The SNP's Westminster leader, Angus Robertson, tells the BBC: "Tony Blair led the country into the worst foreign policy disaster of modern times... Blair says force was 'always an option'. The key issue is when the decision was made for that 'option' to become a grim reality."
BBC political correspondent Laura Kuenssberg says Mr Blair has dismissed the idea that he and President Bush had reached a "deal in blood" at the Crawford ranch to back military action. She says she is "struck" by how often Mr Blair has mentioned 9/11.
At Westminster, one man, believed to be an anti-war protester, has been taken away by police, the BBC learns.
Why are we back to linking Iraq with 9/11? This is just running in circles...Ed, Cambridge
Watching his performance, it's not working for him this time. He's like a rabbit in the headlights. Very nervous and defensive. I think that says it all really.Chic, Leicester
Did I mention Kosovo? That was a great war! Sorry did I mention Kosovo?
Hm, it really doesn't matter if you thought it was right or not.
Blair can be quite icy when he wants to be. "I don't think he (Sir Christopher Meyer) was there at the critical meeting, in fact". Snap.
1152 From BBC political correspondent Iain Watson:
Tony Blair suggests there may be a forward looking - though, for some, not necessarily welcome - aspect to the inquiry - that it is important to learn the lessons of Iraq because of the current problems with Iran; and the suspicion they are developing a nuclear weapons programme.
He's flannelling, trying to mix 9/11 with Islamic fundamentalism and WMD. Saddam was not involved in 9/11, had no weapons of mass destruction and was opposed to Islamic fundamentalism. He's trying to confuse and succeeding!Mike Griffiths, Derbyshire
After 80 minutes, the inquiry is taking its first break for the day. The panel should return at about 1105 GMT.
Saddam was a "menace" to the Middle East peace process, Mr Blair says.
1050 From BBC political correspondent Iain Watson:
Again Tony Blair refutes the "poodle" charge which has dogged him. He says that President Bush would have adjusted their policy of regime change if weapons inspections worked and if the UN route had worked. The term 'UN route' is ambiguous though - some believe the UN route meant disarmament without war, others that it simply meant more explicit and widespread backing for military action. Of course ultimately it led to neither
Former Lib Dem leader Sir Menzies Campbell tells the BBC: "Mr Blair has not once mentioned the question of the legality of regime change. The UN Charter prohibits regime change, but Blair's evidence so far appears to indicate he did not see this as a stumbling block."
Lovely, subtle the arguments the panel are putting forward. Blair can't see it, I doubt anyone else will either. How can Blair say he really really wanted peace in the region, but then he goes and supports an occupation?Richard, Bracknell
There are "very similar issues" with Iran as with Iraq under Saddam, Mr Blair says. The UK is "far better placed" to deal with these now, he adds.
Mr Blair says the US had a tendency to see the Iraq situation and the Israel-Palestine situation separately, whereas the UK saw them as parts of the single issue of peace in the Middle East.
If Blair is saying '9/11 changed everything' then why didn't the coalition go on to neutralise the threat from the real perpetrators in the Middle-East?Rob Miles, Bristol
Yet again Blair starts up with the 'in my view' tack. What about the views of the millions of British citizens who disagreed with him? Why didn't our opinions matter?M J Dolan, Manchester
Back to the Crawford ranch meeting. Sir Roderic Lyne asks whether the US and UK disagreed on the means of tackling WMDs, with the UK preferring the UN route. Mr Blair says that Mr Bush had agreed that "if the UN route worked; it worked".
What the UK confronted was a "new threat" based on a "perversion" of Islam, Mr Blair says. The Middle East peace process is fundamental to dealing with this issue, he adds.
It was clear that, if it came to military action to deal with WMDs, the UK would be "with" the US, Mr Blair says. Force was "always an option", he tells the panel.
1038 From BBC political correspondent Iain Watson:
Tony Blair says the only commitment he gave at Crawford in 2002 was to "deal with Saddam" -and how he was dealt with was an open question, but he believed it was best to go though the UN. Tony Blair's opponents have been alleging he signed up to regime change, although as only Tony Blair and George Bush were present that would be hugely difficult to prove; but Tony Blair says there was "a private note of the meeting". The former ambassador to the US Christopher Meyer says in evidence there was a "tightening" of the position on Iraq and he felt it was significant that Tony Blair mentioned regime change in a speech the next day. Tony Blair said he also mentioned WMD in that speech.
Why is Blair talking as though no-one else was around during the Iraq war? Dude, we were watching you.
Is Blair saying that we went along with America as he didn't want them to feel lonely!
The US and UK have an "alliance", not a "contract", Mr Blair says. He never regarded 9/11 as an attack on America, but an "attack on us", he adds.
The position on Iraq in early 2002 was "open", not "covert", Mr Blair says.
Mr Blair is asked to slow down, as he is speaking too quickly for the stenographer to cope.
There was "no different commitment" made at Crawford, Mr Blair says. He was saying at the time that the UK was "with" the US in dealing with the threat posed by Saddam.
1035From BBC political correspondent Iain Watson:
A key argument from the former PM. Tony Blair attempts to square the circle between regime change and dealing with WMD - he says Bill Clinton in 1998, not just George Bush in 2002/3, was in favour of regime change in Iraq because of the issue of WMD. Britain wanted to deal with WMD, but knew that ultimately this might mean regime change. But the former Foreign Secretary Jack Straw made it clear in his evidence that the justification for any war had to be WMD, not regime change. Tony Blair argues that there should not be a "binary distinction" between WMD and regime change.
I agree with Mike in Newcastle, this man is far too clever to be caught out by an Inquiry with no real power. They cannot even insist on seeing ALL documents pertaining to the inquiry, something they were promised.Paul, Spain
Mr Blair simply cannot give straight answers can he. Nor is he being pressed to give one. This inquiry is looking more and more like a sham.Irfan, London
The only commitment at Crawford, in spring 2002, was to deal with Saddam, Mr Blair says. He and Mr Bush agreed on this, but the method of doing so was "open".
Nothing was decided at one-to-one meetings with President Bush at his ranch at Crawford Texas, Mr Blair says. It was important to have "frank discussions". It was less about "specifics" but the "various different dimensions of the whole issue".
Mr Blair says he and former Foreign Secretary Jack Straw agreed the UK would try to get a UN resolution. He adds that it was important to put together a coalition on Iraq. The UN route was important as he "didn't want America to feel it had no option but to do it alone".
Iraq was quickly becoming the key issue, after the Afghanistan war started in late 2001, Mr Blair says.
1026 From BBC political correspondent Iain Watson:
Tony Blair says he has something to learn from giving interviews in relation to what shouldn't have been a hugely probing encounter with Fern Britton on a Sunday morning show. He says he didn't use the words 'regime change' in that interview. He was asked on the programme if it would have been right to get rid of Saddam even if there hadn't been WMD and he said "you would have to use and deploy different arguments about the nature of the threat" - opponents of Tony Blair interpreted this as sign of his determination to get rid of Saddam come what may. But he tells the inquiry it has been misinterpreted and was not a change of view on his part.
Re:Luke, Northampton, Slippery attitude, give the guy a chance, we have all called for him to come back and discuss what happened. I wish people would get off his backSimon, Northants
#theiraqinquiry looks just like a rehearsed TV show with the banners on the wall and the petitioned off audience. Joke!
Tony Blair will disagree with all the evidence against him using faith & altered perspective to absolve him. Then go home.
1023 From BBC political correspondent Iain Watson:
Sir Roderic suggested that in effect Tony Blair was "attracted" to changing the regime in Iraq as early as March 2002 - if the former PM agreed, opponents would say he then misled parliament which is why Tony Blair very quickly makes it clear the key issue was weapons of mass destruction. Ex-Foreign Secretary Jack Straw made clear last week in his evidence that taking action on disarmament was legitimate, taking action specifically to change the regime would not have been
Mr Blair says that President Bill Clinton came out in favour of regime change in 1998. This was motivated by WMD concerns, he says. The UK was saying it wanted to deal with weapons of mass destruction, and that if this meant regime change "so be it", he adds.
The questioning now moves to panel member Baroness Prashar. She asks what Mr Blair's response was to the US's "shift in policy" on extremism. Mr Blair says the shift "really happened" after 9/11. The UK intended to respond by saying the problem now had to be dealt with, he adds.
Chairman Sir John Chilcot says two new declassified documents will be published on the inquiry's website. Though he gives the impression he does not see them as significant.
A prime minister must take an assessment of risk, Mr Blair says. Pre-9/11 Saddam had been a "monster" but the UK had to "make best". Afterwards, that changed, he adds. Rogue states cannot be allowed to develop or proliferate WMDs, Mr Blair argues.
Blair keeps wanting to elaborate his testimony with past speeches, documentation, books written etc., a bit too elaborate.
Has this just now become a stage 4 Blair to show he was right, where is the questioning, he's going on and on and on.
Mr Blair is asked about a recent BBC interview with presenter Fern Britton where he said it would have been right to remove Saddam without evidence of WMDs. He says it was an interview recorded before the Iraq inquiry's public proceedings began. He says it was "in no sense a change of position".
Saddam's regime, which had used chemical weapons on some of its own people, was a "bigger threat" than many others, Mr Blair says.
The former PM says his Texas speech of 2002 saying Iraq would be dealt with calmly, but that leaving it to develop WMD was "not an option". The issue was "very, very simple", he adds. It was that Saddam did not "continue to defy the international community" on WMD (weapons of mass destruction).
Mr Blair says his Chicago speech of 1999 was not to apply a "moral test" to foreign policy, but to say it was "in our national interest" to see that problems in other parts of the world could "hit us" in the UK.
Sir Roderic Lyne asks whether the removal of regimes had become a "valid objective" of UK policy by 1999. "No," Mr Blair replies. WMDs were the "key issue" in Iraq, he adds.
Most of the worry was about a "humanitarian" catastrophe involving Sunnis and Shias, should Saddam be removed, Mr Blair says. It was important to send an "unremitting" message after 9/11 to regimes engaged in producing WMDS - (weapons of mass destruction).
1010 From BBC political correspondent Iain Watson:
Sir Roderic has been pressing Tony Blair on who he consulted to discuss the options for dealing with Iraq in March 2002, before meeting President Bush. It would appear from his response there was not a full cabinet meeting specifically to discuss the options paper - Tony Blair names Jack Straw, and "the defence secretary" ie Geoff Hoon as key players. No mention of Gordon Brown at this stage. He did say Robin Cook challenged him but the late former leader of the House was not at a meeting at Chequers to discuss the options.
Does Blair expect us to believe that intelligence before 9/11 couldn't already have told us the scope of the threat? Continuing to use this as a reason for the invasion is laughable.Tom, London
People are calling for Blair's head, but the reality is Blair is far too clever and smooth to be put under pressure by this panel. He does a look a bit nervous, but you know he's far too well-prepared to be caught out.Mike, Newcastle
Can anyone else see Blair is trying to direct the committee in his answering questions - to give specific points to questions that are not asked for.Colin, Leeds
At least he's not been running from his decision, like every single other politician.
The "downside" arguments were about the risks of military involvement and to relationships with the Arab world and others, Mr Blair says. The "full range" of views were received, but "the trouble was, we had to make a decision".
Mr Blair says he was "never short" of people challenging him during this period, including cabinet ministers Robin Cook and Clare Short. But the Iraq options paper was not specifically discussed at cabinet, he tells the inquiry.
Mr Blair said he worked closely with former Foreign Secretary Jack Straw and others. The conclusion was that sanctions were not working. They "absolutely" considered the options available, Mr Blair says.
Sir Roderic Lyne, a former Foreign Office man himself, asks what options were open to the government post 9/11. Mr Blair says these were sanctions, Saddam allowing weapons inspectors in. The option of removing Saddam had "always been there". After 9/11, the view was that "we can't go on like this".
Mr Blair says containment through sanctions was eroding and that trade sanctions under revised UN arrangements were being "watered down".
A paper of 7 March 2001 described the arrangements for smart sanctions and urges better control of borders to Iraq. The idea was to seal off the borders around Iraq to make these more effective. The Russians would not back the idea, and it was dropped by May 2002, he adds. Mr Blair says it is "at least as persuasive" an argument that the smart sanctions would have failed, as saying they could have succeeded.
Only a few minutes in and Blair is already trying to manipulate this situation to enable him to make a self promoting speech. What a slippery attitude to take.Luke, Northampton
There is discussion about whether a document mentioned by Mr Blair has been declassified. It is available online in any case, he is told to laughter. Mr Blair says it described containment as a "least worst option". So-called "smart sanctions" were discussed by government, but there was "no guarantee" these would work, Mr Blair says.
On the policy of containment of Saddam, Mr Blair says the Iraqi leader had eroded support for previous sanctions and that food and money provided for food and medicines for Iraqis was being misused. Saddam had been "successful" in blaming the West for the sanctions.
Sir Roderic Lyne says Saddam was not involved in 9/11 or with al-Qaeda. Mr Blair responds that 9/11 changed perceptions.
0951 From BBC political correspondent Iain Watson:
Tony Blair argues that the "calculus of risk" changed after 9/11 from Iraq but also from other countries such as Libya. He gets an early rebuttal in to the charge that he was a 'Poodle' of the US by saying "this wasn't the American position-this was the British position."
Mr Blair says that, in his statement to the Commons on 14 September 2001, he specifically dealt with the issue of weapons of mass destruction. The 9/11 attacks were inspired by "religious fanaticism" and the attackers would have killed "30,000" had they been able, he says. After that time, Mr Blair says it became clear "you could not take risks" and that terrorists would use chemical and biological weapons. This was "not an American position", but the UK's own view, he says.
Mr Blair says the effectiveness of sanctions before 9/11 was eroding. He adds that he has gone back through his speeches during this period. From 1997 to 2001 Mr Blair says the sanctions in place on Iraq weren't the "top priority". If 9/11 had not happened, the assessment of Saddam would not have been the same. The UK and US view changed "dramatically" at this point, Mr Blair says.
0948 From BBC political correspondent Iain Watson
Sir John Chilcot has in effect indicated that the questioning will focus on some of the most controversial areas - Tony Blair's meeting with President Bush in Texas in April 2002 - which some opponents of war suggest that was when the former prime minister really signed up to regime change, and how the case was presented to parliament - opponents say Tony Blair misled parliament by suggesting in a dossier that intelligence on Iraq's weapons programme was 'beyond doubt' rather than sporadic and patchy. A less controversial area will be covered later on - the aftermath of war, where there is abroad consensus - at least in the UK, that this was not handled well initially; Gordon Brown has criticised this and David Blunkett this morning called it 'a shambles'
Today, Tony Blair mainly gets to prove he's a lawyer. He will mainly rely on retrospective justification, and black will be proven white once more.Peter Baker, Zurich
He asks Mr Blair what he thought of the policy of containment of Saddam Hussein before the terror attacks of 11 September 2001. Mr Blair begins his evidence, saying Saddam was a "major problem" in this period, with breaches of the no-fly zone which had been imposed. He says the UK's policy was "doing our best, hoping for the best, but with a different calculus of risk-assessment". After 9/11, this calculus of risk changed, Mr Blair adds.
Panel member Sir Roderic Lyne opens the questioning. He asks how Mr Blair's government developed its broad strategy to Iraq in 2001 and early 2002, together with the US.
Mr Blair could appear again at the inquiry at a later, Sir John Chilcot says, should this be deemed necessary. Today's hearing will focus on strategy towards Iraq up until 2002, including Mr Blair's meetings with former US President George W Bush. The presentation of Iraq policy and the diplomatic efforts in the lead-up to war will be discussed. The aftermath of war will also be dealt with.
Sir John Chilcot sets out the committee's aims to Mr Blair. He says the war has aroused "strong emotions" and that bereaved families are looking for answers. The inquiry is "not a trial", he adds.
The waiting is over. Tony Blair's six-hour question-and-answer session is beginning. The former prime minister looks fairly relaxed, greeting his inquisitors with a "morning", but the butterflies must be there.
Iraq inquiry chairman Sir John Chilcott says he hopes the committee can go through today's evidence in an "orderly way", reminding the audience to behave when Mr Blair arrives and speaks.
No new declassified documents will be released by the Iraq inquiry today, the BBC has learned. Several have been published in the last few days.
Henrietta Heald, one of the members of the public who won tickets to the hearing, via a ballot, says there was a "festival atmosphere" in the queue. Inside the hall, there is a large screen, with "muzak" playing, she adds ahead of Mr Blair's appearance.
0930 From the BBC's Dominic Casciani:
Even with the noisy police chopper overhead and the drizzle, the crowd of a few hundred protesters were enjoying themselves outside the inquiry HQ. There's some megaphone-synchronised chanting, declaring Tony Blair a war criminal, and a makeshift prison cell holding someone with a TB mask and blood on his hands. The photographers from the tabloids cheered up thanks to three young ladies who agreed to high-kick their way through a ditty about weapons of mass destruction. All the demonstrators have decided that, whatever TB says today, he should be put on trial.
BBC political correspondent Laura Kuenssberg says the panel has face criticism about being "too soft" on previous witnesses. It will be under "enormous pressure" to give Mr Blair a tough grilling, she adds.
It has been a dramatic week at the Iraq inquiry so far. Two former Foreign Office legal officials have told the panel they thought the war - without a UN resolution authorising invasion - was illegal. Ex-Attorney General Lord Goldsmith has said he changed his opinion on the matter in early 2003. Mr Blair is likely to be asked about these comments.
Mr Blair's last major public appearance in the UK was his final prime minister's questions session in 2007. On that occasion, he left the chamber of the House of Commons to a standing ovation.
Some of the families of the 179 UK service personnel killed in Iraq will be in the inquiry room at the Queen Elizabeth II conference centre in central London. Hundreds of anti-war protesters have gathered outside the building. Mr Blair arrived at about 0800 GMT.
My colleague Iain Watson will be providing expert analysis of Mr Blair's performance at the inquiry, which is expected to get under way at about 0930 GMT. We will also have contributions from a range of different politicians during the course of the day.
This is the big one. Tony Blair, the prime minister who took Britain to war in Iraq in 2003, is to face six hours of questioning about his role. The five members of the Iraq inquiry will ask him about the build-up to the invasion, the conduct of the war and the planning and execution of its aftermath. There will be particular interest in the legality - or otherwise - of the war and the discussions between the US and Britain before troops were sent in without a second United Nations resolution. Also expect questions about the claim that Saddam Hussein was developing "weapons of mass destruction". You can watch whole session via the video stream at the top of the page, which is on a one minute delay.