NATO Meets on Bombing Renewal : Bosnia: As deadline passes, Serbs move some heavy weapons around Sarajevo to collection sites. Their political and military leaders differ over compliance with West.

NATO warplanes roared over Bosnian Serb strongholds early today as Western military commanders convened a “war council” to decide whether to resume bombing the separatist rebels.

As the deadline for Bosnian Serbs to ease their 40-month siege of Sarajevo passed, there were signs of movement of heavy weapons into collection points in Serb-held suburbs, U.N. officials said. But it was not clear whether that movement was enough.

Under the NATO gun, Bosnian Serb politicians offered to comply with NATO and U.N. demands. Bosnian Serb army commander Gen. Ratko Mladic, however, remained defiant and rejected the West’s ultimatum.

Around Sarajevo, the Bosnian capital, and the Serb stronghold of Pale, nine miles to the southeast, the darkened horizon lighted up with yellow and orange bursts from what U.N. officials said was probably antiaircraft fire launched by the Serbs against NATO aircraft.

The North Atlantic Treaty Organization demanded that the Serbs move their artillery from within a 12 1/2-mile exclusion zone around Sarajevo, allow access on roads into the capital and reopen its airport. Failure to comply, NATO said, would mean a resumption of the punishing air campaign first launched Wednesday in retaliation for a lethal shelling of Sarajevo and then suspended Friday to wait for Serb concessions.

“If they don’t play ball, they will be hit very, very hard,” U.N. spokesman Alexander Ivanko said in Sarajevo.

Despite Mladic’s tough talk, U.N. officials reported “highly unusual movement” of heavy weaponry into collection points in Serb-held suburbs around Sarajevo. It was not clear if the weapons were being withdrawn or simply hidden from NATO eyes. Bosnian Serb television showed pictures of tanks and trucks rolling in the night.

U.N. officials were monitoring the movement to determine whether it was enough to call off air strikes. A decision was not expected until after dawn today.

“The assessment of the latest Serb heavy-weapon movement will take more time,” U.N. spokesman Chris Gunness said in Zagreb, the Croatian capital, early this morning. “NATO remains poised and ready to strike.”

Poor weather and darkness were hampering efforts to assess the Bosnian Serb movement around Sarajevo, officials said.

Throughout the night, as the 11 p.m. deadline came and passed, U.N. force commander Gen. Bernard Janvier, in Zagreb, conferred with NATO’s southern commander, U.S. Adm. Leighton W. Smith, in Naples, Italy, where he presided over a so-called war council to plot strategy.

NATO aircraft remained in the skies over Bosnia-Herzegovina and could launch strikes at 20 minutes’ notice, officials said.

As the deadline bore down on the Serbs, they sent mixed signals.

In a last-minute attempt to block a new wave of attacks, the Bosnian Serbs’ political leadership sent a message to the United Nations indicating that the Serbs were willing to comply with the demands.

And Bosnian Serb leader Radovan Karadzic telephoned former U.S. President Jimmy Carter, who negotiated a four-month cease-fire earlier this year, to say he would comply, according to Carter’s office.

Serbian President Slobodan Milosevic, the onetime patron of the Bosnian Serbs and now their official representative in U.S.-sponsored peace talks, privately contacted U.N. special envoy Yasushi Akashi to give similar assurances, sources said.

But Mladic contradicted that spirit. In a 4 1/2-page letter to Janvier, Mladic angrily replied that he could not authorize withdrawal of his troops or their weapons from around Sarajevo, especially without guarantees that his forces would not be attacked by Bosnian government troops.

“Mr. General, I recommend you replace ultimatums with negotiations and the bombardments with agreements,” Mladic said, according to an unofficial translation of the letter by reporters.

“No one, not even I, has the right to order the withdrawal.”

The split between Karadzic and Mladic is well known, but Mladic’s defiance to the end does not bode well for the negotiations undertaken by U.S. Assistant Secretary of State Richard Holbrooke.

“We don’t know if it’s a bad-cop, good-cop [routine], or if it’s a genuine rift,” said a U.N. official. “Whatever it is, it’s a very dangerous game.”

Through a spokesman, Janvier said Mladic’s latest letter was not satisfactory. It “did not address sufficiently the conditions set forth” by NATO and the United Nations, the French general said.

NATO’s largest military operation ever has tested the will of the West, and the delicate alliance that last week acted swiftly and decisively in favor of the bombings was showing signs of strain.

Janvier on Saturday recommended that air strikes not be renewed, but he was overruled by NATO’s political arm. The NATO ambassadors, in a debate that stretched for nine hours, issued the ultimatum that expired Monday night.

In that meeting, American and French officials were said to have argued for immediate resumption of the bombing, while others were willing to give the Serbs more time.

Several members of the Western alliance have expressed qualms about the perception that NATO is taking sides in the war and about the danger of an open-ended air campaign.

“We have not become a party to the war,” British Defense Secretary Michael Portillo said late last week. “Once we have destroyed the guns or they have been withdrawn, that would have fulfilled the task. We are not involved in hot pursuit, and this is not punishment or retribution.”

The Muslim-led but secular Bosnian government, at first delighted at the decision of NATO and the United Nations to finally take robust action against the Serbs, is now angry over the suspension of the air raids. Government officials have threatened to boycott a crucial meeting of the foreign ministers of Bosnia, Croatia and the rump Yugoslavia designed to be a preliminary step toward eventual peace negotiations.

Holbrooke, the negotiator who brokered the conference scheduled to take place later this week in Geneva, sought to reassure the Bosnians by minimizing the significance of the pause in aerial attacks. “It took us many years to get to this point, and I don’t think a few hours either way is going to make a difference,” he said.

The lull in the air strikes has been used by Mladic to repair some of the air-defense system destroyed in the first bombing runs, NATO and U.S. officials said Monday. Only about 15% of the SAM-6 and other antiaircraft missile batteries the Serbs use were destroyed.

Mladic has been able to repair some of the equipment, and it is back in operation.

U.S. military officials said, however, that the danger from the weaponry can be minimized because air-defense batteries are fixed sites and NATO commanders now know precisely where they are. In addition, the allies can send in fighters with escort planes specially equipped to jam air-defense radar.

Times staff writers Art Pine in Washington and Tyler Marshall in Brussels contributed to this story.