Rebel Serbs Threaten to Wipe Out Gorazde : Bosnia: 65,000 citizens face annihilation unless city surrenders. U.N. convoy is halted north of ‘safe haven.’

Rebel Serbs issued a surrender-or-die ultimatum to the leaders of Gorazde on Thursday, threatening to annihilate the 65,000 civilians trapped in the U.N. “safe haven” unless the Bosnian government capitulates.

Authorities in Gorazde disregarded the 4 p.m. deadline for surrender.

U.N. Protection Force troops had set off for the beleaguered Muslim pocket earlier in the day, but the peacekeepers were halted 18 miles north of the enclave by a blockade of Bosnian Serb women and children in what appeared to be another attempt at securing a human shield against air strikes.

More than 200 U.N. troops and aid workers were taken captive by Serbian rebels last week after token NATO air strikes failed to halt the deadly offensive against Gorazde but succeeded in angering the defiant Serbs.

Most of the hostages have been released as the rebels maneuver to deter a seemingly serious threat of massive air strikes after a call by President Clinton for determined action to stop the Gorazde carnage.

And the U.N. Security Council early today demanded that the Serbian forces pull back from Gorazde and release any remaining hostages.

But even the more severe warnings from Washington and NATO headquarters in Brussels have had no measurable deterrent effect on the Serbs: U.N. spokesman Maj. Dacre Holloway said they launched a major infantry attack on the southern flanks of Gorazde close to nightfall.

The Serbs demanded in the morning that all government troops and civilians withdraw from the enclave to within a 1.8-mile radius of the city center and threatened to “roll over the civilian population” with every weapon in their arsenal unless the Muslim-led forces complied, a senior Sarajevo official disclosed.

The ultimatum was hammered home to the hungry and terrified population by a barrage of tank and artillery shells that killed at least 47 people and wounded 143, according to foreign aid workers hunkered in basement shelters in the besieged city.

Two tank shells tore through a makeshift first aid station near the city hospital that was destroyed a day earlier by wire-guided missiles. Doctors with the international humanitarian group Doctors Without Borders said 20 patients died inside the clinic, which was crowded with wounded.

A doctor at the ravaged facility, Ferid Tutic, told reporters here in a ham radio broadcast that the overwhelmed hospital staff was able to evacuate only seven of the 35 people pinned inside the smoldering clinic.

“We could still hear screams from within the burning building,” the anguished doctor said.

Well over 400 civilians have been killed by the onslaught that the Serbs began in late March. They have pressed on despite token NATO air strikes and threats of escalated attacks. Showing no inclination to retreat when the U.N. mission here is powerless to stop them, the Serbs instead have intensified their offensive.

The commander of the Serbs’ radical Herzegovina Corps used the blocked U.N. convoy as bait to lure the beleaguered homeless into submission, saying the foreign troops and the food and emergency medical care due to follow would be let through only if the defenders surrender.

Bosnian Prime Minister Haris Silajdzic called the ultimatum outrageous and appealed to the international community to make good on its proposals to strengthen the U.N. defense of Gorazde before more civilians were killed.

“The Serbs are trying to buy time. I hope the world will wake up and stop the public execution of so many thousands of innocent people,” Silajdzic said.

The convoy of 100 Ukrainian, British and French troops, along with 41 Scandinavian medics, planned to bivouac for the night along the side of the road at the rebel stronghold of Rogatica, Holloway said.

The U.N. official who negotiated the agreement by which Bosnian Serb political leaders had promised to permit the deployment to Gorazde said there was nothing the mission could do to force its way in.

“It’s simply unacceptable that people sign things, then change their minds,” lamented Viktor Andreyev, U.N. civilian affairs chief.

Andreyev indicated disapproval of the mounting Western pressure for punitive air strikes if the Serbs refuse to pull back but conceded that an escalation of foreign intervention is likely.

Asked if he believed that the U.N. mission was about to be drawn into a cataclysmic clash with the Serbs, he replied: “Yes. I hate it, but it looks like that.”

Bosnian Serb political leaders in the rebel headquarters at Pale, just east of Sarajevo, have sought to justify their assault on Gorazde by saying that it is in retaliation for attacks by the encircled government forces among the enclave’s civilians and refugees.

Serb nationalist leader Radovan Karadzic has also said that government troops used the medical facilities in Gorazde as cover to wage attacks--a contention dismissed as preposterous by U.N. military observers still in the pocket, Holloway said.

In a further sign of defiance, Karadzic issued a statement through Serbian media warning that he would not take part in any further peace talks unless the United Nations lifts economic sanctions imposed on neighboring Serbia, whose government supports the Serb rebels in Bosnia.

The deputy chief of the Bosnian Serb army, hard-line Gen. Milan Gvero, also issued vague threats against U.N. peacekeepers, saying “the aggressor’s personnel would not be safe” on Serb-held territory.

Serb leaders have characterized the U.N. mission as an enemy force since NATO warplanes bombed two rebel positions firing on Gorazde last week.

Gorazde is one of six U.N.-designated safe areas, which the U.N. commander for Bosnia has proposed be accorded better protection through the proclamation of weapons exclusion zones backed by the threat of NATO air strikes.

NATO officials are scheduled to consider the plan today. By pretending to approve the peacekeepers convoy, Serbs may have lured it deep within rebel territory and acquired a convenient pool of potential hostages in the event that NATO approves wider use of air power.

The Serbs have conquered about 72% of Bosnian territory and expelled most non-Serbs since rebelling against Bosnian independence in March, 1992. At least 200,000 people, mostly Muslim civilians, are dead or missing from the conflict.