U.S. Officials Fear Fallout as Bosnia Role Is Boosted : Balkans: Muslims score victories, and Washington begins to worry its efforts will cause friction with allies.

The Clinton Administration, facing a six-month deadline to achieve a negotiated peace in Bosnia-Herzegovina, is acting on several fronts to step up pressure on Bosnia’s Serbian rebels and to support the Muslim-led government after the U.S. decision this week to stop enforcing a U.N. arms embargo against the embattled republic.

Paradoxically, though, U.S. officials have begun to worry not that their efforts might fail but that they might succeed too well.

In recent weeks, the Muslim-led Bosnian army has scored some unexpected victories on the battlefield, retaking territory in western Bosnia that had been seized by the Serbs. Normally that would be good news to U.S. policy-makers, who regard the Bosnian Serbs as aggressors and the government as victims in the ethnic conflict.

But U.S. officials are increasingly concerned that the government offensive could produce unwanted consequences, including new friction between Washington and its allies, a confrontation between the Administration and the Republican-controlled Congress and--in a worst-case scenario--U.S. armed intervention in a Vietnam-style war.

So when the White House announced publicly Friday that President Clinton had ordered the Navy to allow ships bearing weapons for Bosnia to slip through the U.N.-ordered blockade, officials made it clear that this was a reluctant decision, made only because Congress required it.

At both the State Department and the Pentagon, officials fretted that the move might set back their attempts to mediate by putting the United States squarely on one side of the war. And, they noted, it had the unwelcome effect of dividing the United States from Britain, France and other North Atlantic Treaty Organization members, which have been enforcing the embargo.

Secretary of State Warren Christopher summed up the optimistic view: “Our policy is to put pressure on the Bosnian Serbs any way we can. That the Bosnian government may be holding its own helps to put more pressure on the Serbs.”

A Pentagon official added that the decision to stop enforcing the arms embargo “should have a political effect of making it clear to the Bosnian Serbs that the pressure on them will increase--and that they would be well-advised to agree to the Contact Group proposal.”

That proposal--the cornerstone of U.S. policy in Bosnia--is a partition plan advanced by the United States, Russia, Britain, France and Germany that would cede 49% of Bosnia to the Serbian minority and reserve 51% for the federation of the government and the third major ethnic group, the Bosnian Croats.

The government and the Croats have accepted the plan, but the Serbian rebels, who still hold about 70% of the country, have refused.

Despite Christopher’s upbeat assessment, the prevailing view at the State Department is profoundly ambivalent. Government battlefield successes may pressure the Serbian rebels into accepting the Contact Group map, but the chances are at least as good that the offensive will only reheat a war that had been relatively quiet recently, perhaps drawing in outside powers.

“The government’s offensive opens the door for everything to fall flat on its face,” one Administration official said. “We don’t have much control over this situation.”

The official said that the government successes may be evidence that Serbian President Slobodan Milosevic has kept his promise to stop the flow of arms and other supplies from Serbia to the Bosnian Serb forces. And that is regarded as a plus. But if the military pressure on the Bosnian Serbs keeps up, that might cause Milosevic to resume helping them. And that would be a clear setback.

Many non-government experts doubt that the government army has the strength to force the rebel Serbs to accept a negotiated end to the war. These specialists said the government advances may be a welcome change from rebel conquest but they may make the situation even more perilous for the government and for the rest of the world.

“We should be happy about government advances, because they make it less likely that the Serbs will win big against the Muslims,” said Warren Zimmermann, the last U.S. ambassador to the Yugoslav federation before it disintegrated. “I don’t agree that this may shorten the war and bring a negotiated settlement closer, however. The odds are that it will increase the incentive for the Serbs to take some bloody revenge. That would put a negotiated settlement even farther away and produce a war that goes on and on.”

Marten H.A. van Heuven, a former U.S. foreign service officer and intelligence analyst, said government military advances may prolong the conflict.

“If I were a Bosnian Muslim and was hoping to drag the United States into it on my side, I would not want to sign anything now,” said Van Heuven, now a scholar in the Washington office of the RAND think tank.

The Bosnian government offensive is also certain to produce strains between Washington and the U.N. peacekeeping force in Bosnia.

Officials say that if the government registers many successes, the Bosnian Serbs are almost sure to mount a counteroffensive that may target the U.N. force, which includes British, French and Russian contingents but no U.S. ground troops.

If the government registers major victories, the United Nations seems certain to withdraw the peacekeepers, a step that could prove disastrous for civilians, many of them Muslims who depend on the U.N. operation for food and other supplies.

The Bosnian government’s recent advances were possible because the army has lately been able to circumvent a U.N.-imposed arms embargo against all former Yugoslav republics. But the leakage is relatively modest, and the army remains at a disadvantage in heavy weapons to the Serbs, who are unaffected by the embargo because they have access to much of the arsenal of the old Yugoslav army.

Under legislation passed by Congress earlier this year, the Administration must urge the U.N. Security Council to lift the embargo if the Serbs do not accept the Contact Group partition plan by Tuesday. The United States has introduced a draft resolution to end the embargo, but it has no chance of approval, because Britain, France and Russia all oppose it and each has veto power.

The same law required Clinton to stop U.S. enforcement of the embargo--an action that officials said will have little practical effect, since only three of the 19 ships maintaining the blockade are American, and the other NATO countries plan to continue blocking arms shipments to Bosnia.

The law also requires the Administration to draw up a plan for the United States to break the embargo by shipping weapons to Bosnia. Such an action would cause a full-scale crisis between the United States and its allies, and Clinton has refused to take that step--even though he opposes the embargo in principle.

The Republican victory in congressional elections will make Clinton’s awkward position even more difficult.

The incoming Senate majority leader, Bob Dole (R-Kan.), is a leading advocate of breaking the embargo, and Administration officials fear that he will try to force Clinton’s hand with binding legislation.

That could be disastrous, analyst Van Heuven warned.

“If the United States were to unilaterally lift the embargo, we would be assuming responsibility for the Bosnian Muslims,” he said. “ . . . Before you know it, you have going in the Balkans a proxy war in which we are backing one side and Moscow and perhaps others are backing the other side. We could not afford to lose this--so we would escalate.”

On Friday, Britain and France publicly criticized the U.S. decision to stop enforcing the arms blockade as a step toward possibly breaking the embargo.

“It is a worry, because this is a mandatory resolution of the (U.N.) Security Council,” British Foreign Secretary Douglas Hurd said.

French Foreign Minister Alain Juppe issued a statement saying that his government regrets the U.S. action and called for an emergency meeting with Christopher.

Times staff writer Stanley Meisler contributed to this report.