LONDON - Prime Minister Tony Blair said Tuesday that "significant numbers" of British troops could be withdrawn from Iraq within 18 months.

British forces would remain in the war-shattered country for as long as the Iraqi government wished them to, Blair reiterated before the senior members of Parliament who make up the Commons Liaison Committee.

"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," he added.

British and Australian troops in southern Iraq are preparing to leave Muthanna province next month in the first such handover to Iraqi forces.

"What we have discussed in government is how, as progressively the Iraqi forces are more capable of taking over individual provinces, we will withdraw," Blair said.

"If one's talking about substantial troop reductions, I think the Iraqi government are keen to get control of their own security situation."

Britain was the major coalition partner in the US-led invasion of Iraq in March 2003 and has 7,200 troops stationed in the south of the country around the second city of Basra.

Challenged on whether the mere presence of British troops in southern Iraq was aggravating the security problems there, Blair agreed that their presence was "used by certain of the groups".

Iraqi troops were deployed in greater numbers on Basra's streets last month amid fears that the city was descending into factional violence.

Asked if British forces needed to reassess their approach in Basra, Blair said: "What you have got is 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.

"It's a very tough situation there but the important thing is always to say to our own people 'Who are the authentic voice of the Iraqis?' The people they elected will give you the best opinion as to what Iraqis really want."

He added: "What the Iraqis say is yes, we want you to leave as soon as possible, but that possibility is not now."

Blair was speaking during a twice-yearly grilling by the committee on a range of government policy issues.