The alliance is crumbling, and fast: Half a dozen other members are withdrawing troops or intend to. By mid-2008, excluding Americans, there will be about 7,000 troops in the multinational force, down from a peak of about 50,000 at the start of the war 4½ years ago, a new review by The Associated Press shows.
U.S. President George W. Bush - buffeted by opposition in the Democrat-led Congress - says he's committed to gradually reducing the U.S. force from its current peak of 168,000 soldiers to just over 130,000 by next summer.
American troops already are stretched thin trying to contain Sunni and Shiite extremists. But defense experts say the shrunken coalition probably won't make much of a difference because non-U.S. forces have stuck to limited rules of engagement.
"This is a U.S. and Iraqi coalition - nothing more and nothing less," said Anthony H. Cordesman, former director of intelligence assessment at the Pentagon and now an analyst with the private Center for Strategic and International Studies in Washington.
"A British withdrawal and that of other countries really doesn't matter very much. They're playing a very limited role," he said Tuesday.
What's certain is this: The alliance has withered dramatically since its peak in the months after the March 2003 U.S.-led invasion.
At its height, the multinational force numbered about 300,000 soldiers from 38 countries - 250,000 from the United States, about 40,000 from Britain, and the rest ranging from 2,000 Australians to 70 Albanians.
By January of this year, though, the combined non-U.S. contingent had dwindled to just over 14,000. As of Tuesday, it stood at 20 nations and roughly 11,400 troops.
It's in for more unraveling: Prime Minister Gordon Brown said Monday that Britain will halve its remaining force of 5,000 next spring, and another official said there were no guarantees that any British troops would remain in Iraq beyond the end of 2008.
The latest troop pullouts include Denmark, which withdrew its 460-member contingent from the southern Iraqi city of Basra in August and replaced it with a small helicopter unit.
In a recent newspaper interview, Danish Prime Minister Anders Fogh Rasmussen conceded his country and other coalition members miscalculated when they thought "that foreign troops would be welcomed with open arms like liberators." Seven Danes were killed in Iraq.
Latvia also withdrew all but 15 of its 125 personnel, and Lithuania brought home its 50 troops.
But the coalition will fragment further.
El Salvador cut its contingent from 380 to 300 in August, and the country - the only remaining Latin American member of the alliance - has said it expects to draw down further if the situation in Iraq improves.
Georgia said last month it will slash its peacekeeping contribution from 2,000 personnel to around 300 by next summer. Defense Minister David Kezerashvili said the decision was worked out with the Pentagon.
On Sunday, the foreign minister of the Czech Republic said his country was working on a plan to gradually withdraw its 100 troops, who guard a British base in southern Iraq. Their current mandate expires Dec. 31.
The minister, Karel Schwarzenberg, declined to provide details on the timing of a pullout, saying the Czechs still needed to consult with their allies.
Even staunch U.S. partners have caved to growing public and political opposition to get out.
"You have seen this become a globally unpopular war," Cordesman said. "Most of the world sees it as unjust and sees the United States as having effectively lost because it went to war for the wrong reasons."
Yet two key allies - Poland and South Korea - have signaled they'll stand by the U.S.
Polish Prime Minister Jaroslaw Kaczynski said Tuesday his government won't decide whether to withdraw its 900 troops from Iraq until after the 2008 U.S. presidential election.
The Poles have ruled out "escape or desertion, because that would mean losing everything that we've gained," Kaczynski told Polish state Radio 1. "It's going to be necessary to wait on the results of the American elections."
Officially, South Korea is still undecided, and public discontent over its deployment of 1,200 troops runs high. But Bush has pressed President Roh Moo-hyun to extend the mission, and recent South Korean news reports suggest the government appears to be leaning that way.
The U.S. also can count on a handful of smaller stalwarts.
Australia has rebuffed calls by the political opposition to pull out its 550 combat troops from southern Iraq.
Romania, too, says it has no plans to withdraw its 600 peacekeepers.
"This is not a subject," said Valeriu Turcan, spokesman for President Traian Basescu, the nation's commander in chief.