The comments came at a joint press conference in London, following talks between British Prime Minister Tony Blair and Al-Jaafari.

Al-Jaafari also said factors such as building up Iraq's own security forces, controlling its borders and pushing ahead with the political process would all play a part.

"As far as the time needed, I think that depends on many major factors, first the development of the security forces. We are working on this. There are also the borders with other countries in the region. If the countries cooperate with us in controlling these borders, then the time will be shorter."

Tony Blair repeated Britain's commitments to Iraq's security and to the Iraqi people.

"I made it clear that we would stand by our commitment to Iraq and the Iraqi people, that we will make sure that the job we had undertaken is completed and finished. And we were both talking about the need for us all to understand that the defeat of terrorism in Iraq is a defeat for terrorism everywhere."

The meeting came as a car bomb in eastern Baghdad killed at least four people and injured another 16. Also on Monday, two US pilots were killed in a helicopter crash north of the capital.

Around 1,400 people have been killed in Iraq after the new government took office this April.