By Nick Childs
BBC defence correspondent
The Italian government, hitherto one of Washington's staunchest allies on Iraq, has now joined the list of those bowing to domestic pressures and announcing an exit strategy from the country.
Prime Minister Silvio Berlusconi said his country would begin pulling its more than 3,000 troops troops out in September.
Mr Berlusconi qualified his remarks by saying the process of withdrawal would depend on how Iraqi security forces develop.
Dutch troops have already started arriving home
But, with another two key allies, the Netherlands and Ukraine, in the throes of their own withdrawals, the Italian announcement adds to the impression that the much-vaunted coalition in Iraq is unravelling.
A batch of Dutch troops arrived home on Monday. The Ukrainians will be withdrawn by October. The Ukrainian presence has totalled some 1,600 troops, the Dutch about 1,400.
Bulgaria, too, has now said it is looking at pulling its 450 troops out by the end of the year.
As well as the Americans with their 150,000 or so troops, just over two dozen countries have been contributing about 25,000 personnel to the US-led military coalition in Iraq.
The largest foreign contributor after the US has always been the UK, with about 8,000 troops. Some of the contributions have been token in military terms - Norway has a force of just 10, Moldova a dozen. But they have still been an important practical and, even more, a political prop for Washington.
These are not the first departures by any means. Indeed, there have been some acrimonious pullouts before - like those of the Philippines in response to the taking of Filipino hostages in Iraq, and Spain, after the Madrid bombings and the change of government there.
Main international troops in Iraq
South Korea: 3,600
Source: Global Security
The concern in Washington must be that Italy's move could accelerate the process. There is no doubt that this is uncomfortable for the Bush administration.
Equally, there is no doubt that, with the passage of time, the pressures on the coalition partners, many of whom have made commitments in the face of strong opposition at home, have steadily mounted.
The US itself has had to grapple with the problem of having to keep many more troops in Iraq for far longer than it originally planned, at a much higher cost than expected in terms of lives and money.
Washington would almost certainly have preferred that those leaving now did not.
Eighteen Ukrainians have lost their lives in the conflict
But the withdrawals now may be less awkward for the coalition than they would have been, say, six months ago.
There will be some strains. British troops are having to fill in the gap left by the Dutch. And the US-led multinational force may have to draw on reserves to make up for shortfalls elsewhere.
Of course, many of the foreign forces in Iraq have been there under very specific, and often restrictive, rules of engagement.
Iraqi reliability question
That has complicated the lives of the US commanders, who have on occasions had to rush US forces into hotspots when the insurgency has flared, because the particular foreign contingent in place was not allowed by its national authority to carry out the mission the commanders needed.
That is not to belittle the contributions. Among the foreign casualties have been, for example, some 20 Italians and 18 Ukrainians - which have only added to the strains on their home governments.
But the whole emphasis of the security effort is shifting now.
There may still be major question marks over the reliability of many of the new Iraqi security forces. However, the Americans say there are now some 140,000 trained Iraqi security forces. They may not all be fully capable, but the current focus is very much on giving them a greater role.
Washington also points now to the new Nato-led training effort as one of the ways ahead.
It is clearly hoping that these efforts, plus a belief that the political process in Iraq is genuinely moving ahead now, will allow the foreign military - even the Americans themselves - to take more of a back seat.