Serbs Demand the Surrender of Bihac : Balkans: As rebels close in, they threaten annihilation of town’s defenders. U.N. peacekeepers say they cannot prevent takeover, cite missile peril to NATO air strikes.

Serbian nationalists besieging the Bihac “safe area” in Bosnia-Herzegovina on Saturday ordered its Muslim defenders to surrender or face annihilation--a catastrophe the U.N. peacekeeping mission said it was powerless to prevent.

Bosnian and Croatian Serb rebels have positioned surface-to-air missiles around their artillery emplacements to ward off NATO air strikes aimed at halting their onslaught, said an official at U.N. Protection Force headquarters here.

“The most critical thing about Bihac is that there are SAM batteries to the south, which makes it a bit of a deterrent for us, and it’s critical for NATO as they risk having their planes shot down,” said the official, who spoke on condition of anonymity. “From a tactical and technical point of view, there is little UNPROFOR can do.”

Two British Tornado fighter planes were fired at Saturday with one surface-to-air missile as they flew a routine air patrol over the Serb-held town of Donji Vakuf in central Bosnia, reported Capt. Jim Mitchell, a spokesman at NATO’s Southern Command in Naples, Italy. Neither plane was hit, and NATO made no immediate threat of retaliation.

The U.N. mission’s decision to hold fire as Serbian gunmen advanced deeper into Bihac outraged Bosnian Prime Minister Haris Silajdzic, who accused the U.N. special envoy for the Balkans, Yasushi Akashi, of condemning those in the purported safe area to death.

“Mr. Akashi is responsible for the deaths of 70,000 people in (the city of) Bihac,” Silajdzic told reporters in Sarajevo, the Bosnian capital, after reportedly being told by NATO that no protective air strikes could be launched because the U.N. authorities “do not want to turn the key.”

U.N. commanders in Bosnia and officials of the North Atlantic Treaty Organization operate a “dual-key” approach to using air power, meaning that both forces must endorse any air strike.

Silajdzic said he had appealed to NATO Secretary General Willy Claes to take action to protect civilians in Bihac but was told the Western alliance was powerless to move without U.N. support.

Bihac’s mayor, Hamdija Kabiljaqic, said the city’s residents were in panic. If Bihac fell overnight, he told news agencies, there would be a “slaughter.”

A senior U.N. civilian affairs officer in Sarajevo acknowledged to journalists there that the mission had failed in its task of maintaining the six U.N.-designated safe areas for civilian victims of the 32-month-old war.

“It’s quite clear that we have failed to deter an attack on the safe area,” Colum Murphy said. “We were supposed to deter attacks on civilians and to protect the civilian population.”

Continued heavy fighting was reported in and around Bihac a day after NATO warplanes were summoned to conduct air strikes against the besieging rebels, only to be called back before dropping their payloads.

Some U.N. commanders fear that flexing NATO’s military muscle might bring reprisals against peacekeepers in Bosnia.

“There is a limit to how much force we can use in a peacekeeping mission,” Lt. Gen. Michael Rose, the U.N. commander in Bosnia, told the British Broadcasting Corp.

Although the rebels continued to ignore repeated U.N. warnings to cease attacks on Bihac, there was no call for NATO air power Saturday, U.N. mission spokeswoman Claire Grimes said.

Aid workers and Bosnian officials told news agencies that the Serbian rebels resumed their heavy artillery pounding of the safe area at daybreak.

But Grimes said U.N. military observers in the area judged the detonations to be Serbian antiaircraft rockets being fired over, rather than into, the safe area.

“They are exploding in midair. It’s not shelling. Maybe they are being used for effect, to scare the 5th Corps,” Grimes said, referring to the Bosnian government troops from the Bihac region.

During the 3-week-old Serbian assault on Bihac, which followed a dramatic breakout of Bosnian government troops from the pocket and their capture of some strategic territory, the rebels have grabbed back all that they lost and about one-third of the U.N.-designated safe zone. Thousands of Muslims from the seized area fled in panic into Bihac’s crowded city center.

Conditions were described as “desperate.” Refugees huddled in cellars and shelters in Bihac, which has been cut off from most humanitarian aid since May by the Croatian Serbs who control the territory west and north of the pocket and have been backing the Bosnian Serbs, who hold all land to the east and south.

U.N. actions in regard to Bihac were being limited to diplomacy, Grimes said, noting that a civilian official had traveled to Bosnian Serb headquarters in Pale, near Sarajevo, to press the rebels to agree to a cease-fire.

In New York, the U.N. Security Council met in emergency session Saturday and adopted a statement condemning the Serbs’ “flagrant and blatant” entry into Bihac and calling on all parties to negotiate a cease-fire.

The council said the cease-fire should be pursued as part of an overall settlement for Bosnia proposed by the five-nation “Contact Group” on the Balkans conflict--the United States, Russia, Germany, France and Britain.

And three U.S. warships carrying 2,000 Marines were headed closer to the region. The Pentagon had announced Friday that it had dispatched the troops to the Adriatic Sea to help rescue peacekeepers if necessary.

Rebel Serbs took more than 250 Canadian, French, Russian and Ukrainian U.N. peacekeepers hostage Thursday to deter threatened air strikes. And 1,200 Bangladeshi soldiers have been trapped in the Bihac area in northwestern Bosnia for days.

But the touchiness of any American involvement in the Bosnia morass was demonstrated once more when Sen. Nancy Landon Kassebaum of Kansas, one of the most international-minded Republicans in the Senate, objected to the deployment of Marines even to evacuate U.N. peacekeepers.

Kassebaum, interviewed on CNN’s “Evans and Novak” program, said, “We have said we weren’t going to send ground troops in.” Asked by Rowland Evans, “So you do not think any Marines should go ashore?” she replied, “No, I don’t, under the circumstances.”

At the United Nations, where U.S. Ambassador Madeleine Albright briefed the Security Council about the deployment, a U.S. official said the Marines were dispatched only as “a precautionary measure” in case protection or evacuation of American, allied or U.N. personnel is necessary.

Bosnian Serb leader Radovan Karadzic derided the move, telling reporters: “(They) send 2,000 Marines, then they have to send 10,000 more to save the 2,000 . . . that’s the best way to have another Vietnam.”

The Bosnian Serb military hierarchy had demanded that Bosnian government forces defending what is left of the Bihac enclave surrender by 8 p.m. Saturday, local time.

“You are completely surrounded,” chief of staff Gen. Manojlo Milovanovic said in an ultimatum broadcast by rebel-controlled television. “If you don’t want to think about your lives, you ought to think about the lives of your civilian population.”

The U.N. mission had no immediate reports on what transpired after the deadline passed.

Aid workers with the Office of the U.N. High Commissioner for Refugees in the pocket reported heavy fighting around Bihac’s hospital, which is thronged with wounded, said the refugee agency’s Zagreb spokesman, Peter Kessler.

Fighting and “ethnic cleansing” have already displaced 2 million people in Bosnia and eft 200,000 dead or missing.

Times staff writer Stanley Meisler in Washington contributed to this report.