Ned Parker, Times Correspondent in Baghdad, says today's outline timetable for the withdrawal of UK troops from Iraq highlights America's reluctance to set any deadlines.

"It's interesting what has been said on Tony Blair's aircraft about troop withdrawals, because the Americans are being much more guarded about the process.

"Zalmay Khalilzad, the US Ambassador in Iraq, said at the weekend that the formation of the Government will allow for the Americans to start a gradual withdrawal of troops. But in Washington last week Donald Rumsfeld, the Defence Secretary, declined to give any firm timetables. Likewise Condoleezza Rice, the Secretary of State, said yesterday that she couldn't talk about a timetable for withdrawal.

"Unfortunately, the fact that the Americans are giving mixed signals is discouraging for Iraq's Sunni population, which has been leading the insurgency. Many Sunni factions argue that they are simply fighting the US occupation and will put down their weapons when the Americans leave so if they get a clear indication on the timetable then a large section of the insurgency would stop fighting.

"I spoke this morning to Tariq al-Hashemi, the new Iraqi Vice-President, and he described Dr Rice's comments as a real setback. The fear is that Sunni groups will take those comments as a reason not to get involved in the political process - they fear that the Americans will stay forever.

"There are a couple of reasons for the American reluctance. When you look back at the path to war and the decision to go into Iraq, one of the motives of the Defence Department was to restore America's defence capability and its reputation - that this was no longer the America of the 1990s, when US troops left Somalia, or the 1980s, when they left Lebanon after the bombing there. Now they are the strong man, going into Iraq and taking out Saddam Hussein.

"So even if they feel that the time is ripe for withdrawing, even if it's practical and pragmatic, I think they fear that announcing a timeline would allow the Islamic militants and al-Qaeda to claim victory, to say here's the proof of our victory. That is a large part of it.

"The other reasons are that Iraq is still such a dangerous and unstable place at the moment that the only thing holding it together is the US troop presence. American might is limited, but the sheer fact of 130,000 troops on the ground serves as an anchor. You pull the Americans out and the whole thing risks imploding.

"The figure that has been mentioned is reducing the US contingent to 100,000 by the end of the year, but that entails a risk - it wouldn't take much to set the whole place on fire, which would be a heavy blow for the Bush Administration.

"That's happened already, in the spring of 2004, when they were trying to scale down their troop levels from around 130,000 or 140,000 to around 105,000 and then you had an uprising in Fallujah and the first Moqtada al-Sadr uprising. They've been burnt once trying to reduce troop levels and they don't want to be burnt again.

"The British withdrawal plans are also a bit optimistic. British forces are in four provinces, Basra, Dhi Qar, Maysan and Muthanna and a senior official accompanying Mr Blair to Baghdad said that the UK hoped to withdraw its troops from the last two in the next few months.

"I think Dhi Qar and Muthanna might be possible, but it's more tricky for Maysan and Basra. Everything depends on Basra and if you do not have Basra as a safe province then the south remains destabilised.

"Right now Basra is a mess in terms of criminality and violence within the Iraqi population - it's becoming a third world city. Basra also has a very strong contingent of the al-Mahdi Army, al-Badr's militia [a Shia Muslim militia], and that spills over into Maysan.

"It might depend on where the troops go. British officials have talked about bolstering the British troop presence in Basra as they scale down elsewhere, so perhaps that is the answer."

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