Significant numbers of British troops could start leaving parts of Iraq over the next 18 months, Tony Blair says.
Mr Blair says the Iraqi government is keen to control security
But UK forces will remain in Iraq for as long as the government there wishes them to, he told the Commons Liaison Committee of senior MPs.
Tory Edward Leigh challenged Mr Blair over the number of Iraqis who had died since the invasion and asked whether life really was better than pre-war.
The PM said said the deaths were caused by the actions of a criminal minority.
The exchanges came as Mr Blair was asked about the timescale for total withdrawal of UK forces from Iraq.
He said: "I suspect over the next 18 months there will obviously be opportunities to draw down significant numbers of British troops because the capacity of the Iraqi troops will build up."
As Iraqi forces become more capable of taking over individual provinces, "we will withdraw", he said.
"If one's talking about substantial troop reductions, I think the Iraqi government are keen to get control of their own security situation."
He said the Iraqis want UK forces "to leave as soon as possible, but that possibility is not now", adding: "They are the best judge of this."
Pressed over whether the UK may need to reassess its approach in Basra, its main area of operation, Mr Blair said: "You have got the extremists on both sides. Both of them have got the same aim, to prevent the democratic government having its writ run.
"They may use in Basra the presence of British forces as an excuse, but that's not really their aim. Their aim is to get political and security control of Basra so they can run it rather than have the democratic government run it.
"If they say to us we are better off without you, we will go. But that's not what they are saying."
However, Mr Leigh, chairman of the influential Commons public accounts committee, said thousands of Iraqis had died since the conflict, and while he had been able to walk around Baghdad safely in Saddam's time, no-one could do the same now.
Mr Blair said that was because Mr Leigh was a Westerner and not an Iraqi who disagreed with the former dictator. If he had been an Iraqi who disagreed with Saddam Hussein he would have ended up in a mass grave, said Mr Blair.
On the Iraqi deaths, the prime minister snapped angrily: "They are not dead as a result of this invasion or the removal of Saddam.
"They are dead as a result of the actions of a criminal minority. Our job is to stand with the Iraqis against the terrorists."
Mr Blair said the politicians he talked to in Iraq had been elected by Iraqis, and said if people had wanted to they could have voted for the "Saddam party".
Mr Leigh asked when was the last time Mr Blair had spoken to a private soldier without their officer listening, or an ordinary Iraqi.
The prime minister replied: "Excuse me, Edward, I talk to soldiers certainly a lot of the time.
"And the soldiers who are out there have a very clear view of the validity of what they are doing. It's true I don't get to talk to many ordinary Iraqis."
But he said he had recently met eight Iraqi MPs. "Why on Earth shouldn't we stand alongside them to help them get the democracy they want?" he said.
"Why shouldn't people [Iraqi] people have the same rights as everybody else? Surely it's the job of the international community to be behind them."