NEWS ANALYSIS : The 7 Can Agree, Except for Details : Allies: Key questions are in dispute over who might send troops to Bosnia--and who would command them.

The stern warning to Serbia by the world’s seven biggest economic powers Tuesday showed that the Cold War’s old allies can still pull together in a crisis--but it also revealed them to be divided over how to meet the burgeoning military threats of a new, more complicated world.

President Bush, German Chancellor Helmut Kohl and the other leaders at the annual Group of Seven summit said their joint action on the former Yugoslavia is critical. What happens there, they said, could set a pattern for dozens of other ethnic conflicts simmering in Eastern Europe and the former Soviet Union.

But the summit powers were unable to go much beyond declaring their intention to send U.N. relief convoys by road into the former Yugoslav republic of Bosnia-Herzegovina and warning that attacks on the convoys would prompt the U.N. Security Council to “consider” using military force.

The allies were still arguing over almost every concrete question that would arise if the Security Council decided that force was needed: Who would send troops? Under what rules would they fight? And under whose command would they march?

“Those details still have to be worked out,” German Foreign Minister Klaus Kinkel said.

Some of the disagreements are merely tactical. Italian Foreign Minister Vincenzo Scotti said his country, which faces Yugoslavia across the Adriatic Sea, favors a naval blockade; U.S. National Security Adviser Brent Scowcroft said a naval embargo would probably be useless.

But other differences reflected a more important problem for the allies: an increasingly polarized debate over who will manage Europe’s peace and security as the end of the century nears, with the United States on one side of the issue and France on the other.

Those disputes could make raising a multinational force for Bosnia more complicated than the U.S.-led assembly of a similar force to confront Iraq in 1990.

“We’re pretty much in sync with the British and the Germans,” a senior U.S. official said. “But the French have their own agenda.”

Diplomats say the issue centers on the struggle to design a new “architecture” for the defense of Europe--meaning a new set of institutions and arrangements to succeed the North Atlantic Treaty Organization, which put Western Europe under an American military umbrella.

At the moment the problem isn’t too little architecture but too much. The United States and its allies have sketched several competing blueprints for their mutual defense, and they often seem to be working from all of them at once.

In the case of Yugoslavia, Bush and his aides want to get NATO involved in the peacekeeping operation in some fashion. France, which has always considered NATO too American-dominated, wants to give more responsibility to the Western European Union, a defense group that excludes the United States.

That issue will be debated in a broader sense Thursday at a summit meeting of the Conference on Security and Cooperation in Europe, the 52-nation security forum that includes every country in Europe plus the United States and Canada.

The Bush Administration and most of its allies want the CSCE conference to declare that NATO is the appropriate organization to handle peacekeeping duties in Europe. France, which is a member of NATO’s political alliance but not of its military command, opposes giving that mission to NATO.

A U.S. official said the Administration explored the idea of using NATO peacekeepers in Yugoslavia as long as a year ago, before fighting broke out in Bosnia-Herzegovina. But the idea went nowhere because of opposition from France and Germany, he said.

When Bush and French President Francois Mitterrand met for dinner on Sunday night, Mitterrand assured Bush that his aim is solely to strengthen Europe’s ability to defend itself, not to push the United States out of the Continent, officials said.

Bush replied that he was “reassured,” officials said--but U.S. aides remained skeptical.

The Yugoslav crisis has also raised the question of whether Germany and Japan, the world’s second and third economic powers, would join a military expedition--something they were unwilling to do in the Persian Gulf War.

A U.S. official said Germany would probably send troops to Bosnia to act in noncombat roles, in keeping with a clause in the German constitution that forbids deploying combat troops abroad.

Japan was one of the seven summit nations that signed Tuesday’s declaration, but the Tokyo government would probably stay out of any action entirely, just as it did in the Gulf War.

“Legally, we are prohibited from participating in that kind of activity,” Deputy Foreign Minister Kunihiko Saito said. When reporters asked whether Japan’s new peacekeeping force law would allow its troops to participate, Saito said--without much conviction--that his government might consider some non-military role.

The command of the force is another unsettled issue. The United States took overall command of the multinational force in the Gulf War because it had the largest number of troops on the ground. But if a force is sent to Bosnia, Bush and other officials have said the U.S. role would be in the air and at sea, not on the ground. In that case, some European officials said, a non-American should command the force. “We’d be comfortable with that,” a senior U.S. official said.

The uncertainty is in part a product of the new role of the United States as just another big country--first among equals, perhaps, but no longer the undisputed leader in every conflict.

In past crises, the question of who would command a multinational force would hardly arise. But the Bush Administration decided in 1990 that the European Community should be allowed to take the lead in Yugoslavia. U.S. officials have since expressed impatience with the Europeans’ efforts, and Secretary of State James A. Baker III has publicly prodded them several times to do more. But at no point has the Administration stepped up and volunteered to take over completely.

“The EC was in front for a long time on this,” Baker said. “We’re now, all of us, in it together.”