U.S., Allies Mull More Strikes as Serbs Hit Bihac : Bosnia: NATO may use air power again to thwart rebel attacks. Washington pushes for ‘exclusion zone’ to protect enclave.

The United States renewed consultations with key allies Tuesday over possible new air strikes to protect the Bosnian town of Bihac, as Serbian nationalists closed in on the area after Monday’s Western attack on a Serbian-held airstrip.

Clinton Administration officials said the United States is again pressing the United Nations to call in more warplanes from the 16-country North Atlantic Treaty Organization to prevent the fall of Bihac in the face of the intensified Serbian onslaught.

At the same time, Washington was said to be renewing its push to get NATO to declare Bihac an “exclusion zone.” The designation would prohibit the Serbs from using tanks and artillery in the area and would authorize air strikes against violators.

The Serbian attacks on Bihac underscored the difficulty for the Administration and its major European partners in the face of a continuing split among the allies, and between the United Nations and NATO, over how to handle the situation in Bosnia-Herzegovina.

Despite Monday’s NATO air strike against a Serbian-held airfield in Croatia, Serbian forces continued to press in on Bihac, engaging in hand-to-hand combat with Bosnian government troops and setting villages on fire.

Bosnian Serb leader Radovan Karadzic, angrily denouncing NATO as “a criminal organization,” threatened to retaliate against U.N. and NATO forces in a way that “will hurt every member” of NATO.

U.S. officials described the situation in Bihac as “growing more desperate by the minute,” with Serbian rebels mounting a three-pronged pincers movement that sent hundreds of refugees streaming out of the enclave.

They said that Bosnian President Alija Izetbegovic called in U.S. Ambassador Victor Jackovic in Sarajevo late Tuesday to express “very deep concern” about the possibility that Bihac might fall, providing a major setback for Western peacemaking efforts.

The renewed Serbian attacks appeared intended to call the West’s hand following Monday’s NATO air strike on the Serbian-held airfield at Udbina. Damage from the raid was modest. The NATO armada of 30 warplanes blew five craters in the airstrip’s main runways. But Western officials said the raid was designed to “send a signal” that the United Nations would not tolerate the Serbian offensive.

Still, for all their obvious embarrassment in the face of the new Serbian attacks, it was not immediately clear what the allies would do to prevent the fall of Bihac or to ward off any further Serbian retaliation against U.N. forces.

The North Atlantic Council, NATO’s major decision-making arm, is scheduled to meet today to consider a U.S. proposal to create a new “exclusion zone” around Bihac, but officials said Britain and France still are reluctant to go along.

Key European allies have been opposed to increased use of NATO military power because they fear that the Serbs would retaliate and endanger U.N. peacekeeping forces, which comprise mainly French, British and Dutch soldiers.

The Europeans regard Washington suspiciously, partly because the United States has no ground forces in Bosnia and also because they regard it as overly aggressive in its efforts to punish the Serbs.

Even so, top Administration officials renewed their push for the new plan. U.S. Secretary of State Warren Christopher had “extensive” telephone conversations on the issue with French Foreign Minister Alain Juppe and British Foreign Secretary Douglas Hurd.

The Administration also pursued the issue in the United Nations, but apparently failed to win a consensus.

Defense Secretary William J. Perry warned that if the Serbian nationalists launch additional air strikes against Bihac from the Croatian airfield, NATO warplanes will return and destroy the 15 or 20 Serbian fighters that they intentionally did not attack Monday.

Yet time appeared to be running out. Some U.S. officials believe that, unless some action is taken soon, the fall of Bihac could be imminent.

Karadzic’s intensified rhetoric was not the only sign of heightened defiance. Serbian forces near Banja Luka fired two SA-2 surface-to-air missiles at British Harrier aircraft patrolling the area for NATO.

Serbian forces in one area were supported by a rocket-firing helicopter. And the Serbs briefly captured two Czech soldiers attached to a local U.N. peacekeeping force but released them after appeals by the United Nations.