The UN will play an "important role" in post-conflict Iraq and not limited to humanitarian functions, according to Tony Blair and UN General Secretary Kofi Annan.
The UN role should cover 'political and reconstruction issues'
The prime minister, who met Mr Annan at the European Union summit in Athens, said he would like to see the US, UK and Europe "working in partnership" to rebuild Iraq.
Mr Blair said, during a day of discussions with European leaders, he believed there was enough "goodwill and the right spirit" to carry this through.
But he stressed: "Of course it requires give and take on all sides."
Mr Blair, who is trying to repair relations after splits in Europe over war in Iraq, said: "I don't think anyone has said the role of the UN should be small.
I would like to see the US, ourselves, Europe, working in partnership together
"What we're saying is there should be an important role for the UN."
This role would cover humanitarian aid but also political and reconstruction issues.
"I think everyone is agreed, frankly, that the primary interests are those of the Iraqi people," said Mr Blair.
"What they need is a country that is rebuilt after years of Saddam's rule. They need to have proper representative government.
"They need the proper protection of human rights and that government needs to be seen as representative both by the Iraqi people and by the international community.
Straw says the UK and US could go it alone
"I think if we approach the thing in the right spirit of goodwill, we will make sure the situation is handled well, not just on behalf of the Iraqi people, but also in respect of the UN too."
He added: "These are the people that have been freed from years of tyranny. They have gone through an immensely difficult conflict, they need help rebuilding their country.
"The international community, including ourselves, has got a responsibility to do that.
"I would like to see the US, ourselves, Europe, working in partnership together to make that clear."
Mr Annan said: "I am confident that the UN will play an important
role and as we move ahead in the next few weeks I expect that role to become much clearer."
He added that the UN needed to also work with countries in the region "because Iraq and its neighbours will want to live in peace so what happens in Iraq is of interest to the region as well".
Earlier, Foreign Secretary Jack Straw warned that the UN could be sidelined for a second time over Iraq unless Security Council members cooperate on its post-war future.
Mr Straw said Britain and the US could make alternative arrangements unless there is a consensus.
It was the first time Britain had hinted it may be prepared to sideline the UN over Iraq for a second time.
The BBC's diplomatic correspondent Bridget Kendall, who is travelling with Mr Straw, said the warning was clearly intended to increase the pressure on France, Germany and Russia.
The charm offensive to win over European leaders began on Tuesday, when the prime minister met German Chancellor Gerhard Schroeder - who stood alongside Russia's Vladimir Putin and France's Jacques Chirac as the staunchest opponents of war.
Following their meeting in Hanover, Mr Blair and Mr Schroeder presented a united front and said they were agreed on the need for the UN to be involved in Iraq.
In Iraq itself a US-organised meeting has been held on the shape of a future government, with delegates agreeing that the country must choose its own leaders.
France and Russia could, in theory, block new resolutions needed to give post-war Iraq international legitimacy.
I believe that there is agreement, that in principle the United Nations must have a key role
During the two day summit the prime minister was expected to outline his vision for a full-time EU president, responsible to the
member governments, giving the EU "strategic direction".
The plan is likely to bring him closer to both France and Germany, who back the idea.
He argued that an enlarged EU of 25 member states needed a more powerful
voice on the world stage than the current rotating leadership.
One government official summed up the position by saying the EU figurehead would be "someone the White House
An "Accession Treaty" was formally signed at the meeting, ushering Hungary, Poland, the
Czech Republic, Slovakia, Slovenia, Estonia, Latvia, Lithuania, Malta and Cyprus into the EU.