BRUSSELS, Belgium -- Shiite militiamen drove Ukrainian soldiers and coalition officials from the Iraqi city of Kut on Wednesday, and Japan urged the United Nations to intervene to stop the growing violence in Iraq.

Italy's defense minister, however, said Italian troops would stay in Iraq, rejecting opposition calls to pull out after clashes that left 15 Iraqis dead and a dozen Italians injured. U.S. forces sent helicopters and troops to reinforce the Bulgarians.

Fighting between coalition forces and Shiite militiamen across a wide swath south of Baghdad presents a major test of the resolve of America's partners to stay the course in Iraq.

The mounting unrest, triggered by the U.S. crackdown on firebrand Shiite cleric Muqtada al-Sadr, will also test the American strategy of avoiding traditional alliances and international institutions in favor of "coalitions of the willing" in a military conflict.

Washington's inability to bring its major partners in the NATO alliance into the Iraq conflict means the United States has no ready pool of well-trained reinforcements -- apart from its own troops -- in case the Pentagon decides more forces are necessary to maintain order.

Instead of binding treaty obligations, Washington must rely on arm-twisting and powers of persuasion to hold on to its coalition partners, some of whom face domestic pressure to send their troops home.

Since violence erupted Sunday in Shiite areas south of Baghdad, coalition soldiers from Europe and Latin America have come under armed attack after months in which the Americans have born the brunt of the fighting -- and the casualties.

But the uprising by al-Sadr's supporters has put the allies squarely on the front lines.

In Kiev, the Ukrainian Defense Ministry said its troops evacuated about 20 coalition representatives -- Americans, Britons, Poles and others -- from the Kut City Hall after Shiite fighters launched mortar and infantry attacks overnight. The civilians and Ukrainian forces moved to a camp outside of town.

"There were no Ukrainian casualties, but several dozen militants were killed," ministry spokesman Lt. Col. Andriy Lysenkohe said.

Elsewhere, Polish troops killed an al-Sadr aide, Muntadhir al-Mussawi, in a shootout Wednesday in Karbala, Shiite officials said. Later, mourners carried away al-Mussawi's body, chanting, "Today we will free Karbala from the Jews."

Spanish commanders convinced Shiite tribal chiefs and clerics to urge al-Sadr to end the takeover of police stations and religious shrines in the holy city of Najaf, Spain's Defense Ministry said Wednesday.

But the statement added that "a stable situation has not yet been achieved."

By Tuesday night, the toll from the Shiite fighting included three dead -- one soldier from El Salvador, another from Ukraine and a civilian truck driver from Bulgaria. At least 12 Italians, five Ukrainians, four Bulgarians and two Poles have been wounded.

Those numbers pale alongside American losses -- 417 battle deaths and about 3,000 wounded since the war started in March 2003.

However, coalition partner losses are significant in smaller countries where support for the war has never been as strong as in the United States, Britain or Australia.

In Tokyo, Japan's top government spokesman, Yasuo Fukuda, urged the United Nations to intervene "at an early stage" to stop the violence.

"Rather than simply using force, we can consider other ways to stop the violence," Fukuda said without elaborating.

Since the explosion in the Shiite areas, none of the coalition partners have spoken of abandoning the mission. Before the flare-up, however, the incoming Spanish government announced it will withdraw its 1,300 troops unless the United Nations takes over the mission by June 30, when Washington returns power to a new Iraqi government.

In Rome, Italian Defense Minister Antonio Martino told a parliamentary committee that it was "unthinkable" to talk about ending the Iraq mission before the transfer of power to the Iraqis was complete.

Bulgarian President Georgi Parvanov called an emergency meeting of top military officials on Wednesday in the capital Sofia to review the situation in Iraq and the security of the Bulgarian soldiers stationed in the Shiite holy city of Karbala.

Afterward, Defense Minister Nikolai Svinarov said four U.S. helicopters and a U.S. military police platoon have been sent to Karbala to help the Bulgarian troops.

However, signs of trouble are emerging in coalition ranks and are likely to be fueled by the spreading conflict.

On Tuesday, however, several leading Dutch politicians called for a parliamentary debate on Iraq next week. The Dutch government favors keeping its 1,300 soldiers in Iraq after their tour ends July 1.

"It's not a foregone conclusion that we'll stay in Iraq," Dutch politician Boris Dittrich said.

In Norway, an opinion poll released last week showed that 51.2 percent of the 1,505 people surveyed wanted the country's 150 troops home. The margin of error was 5 percent.

Even before the latest fighting, calls for withdrawing Ukraine's 1,650 troops have been increasing because of public concern over the country being targeted for terrorist attack. Three other Ukrainian soldiers have been killed since the Iraq mission began last year.

Thailand's embassy in Sweden received a letter threatening terrorist attacks in the Southeast Asian country if it does not pull its 450 military personnel out of Iraq, the Thai Foreign Ministry in Bangkok said Wednesday.

After failing to win support in the United Nations for a military strike against Iraq, the U.S. administration cobbled together a coalition of nearly 40 countries, which sent a total of about 24,000 troops.

Notably absent are France and Germany, both of which opposed the war.

Even if Washington can hold on to most of its partners, it is unlikely they would be able to provide thousands of new troops if more are needed.

During a news conference Tuesday, Defense Secretary Donald H. Rumsfeld held out the prospect of a role for NATO, telling reporters that "I suspect we'll see, would be delighted to see, NATO take a larger role ... in Afghanistan, then Iraq."

Last week, however, NATO foreign ministers showed little enthusiasm for getting deeply involved in Iraq unless a sovereign Iraqi government asks the United Nations to assume a major role.