Bosnia Serb Forces Ringing Sarajevo Begin Pulling Out : Balkans: U.N. reports artillery convoys moving away. It is seen as ‘heartening sign’ that rebels may comply with ultimatum. Russian diplomatic effort may have been key.

Bosnian Serb forces Thursday began what U.N. observers called a massive withdrawal from mountaintop artillery nests ringing Sarajevo, offering the first serious sign that they may comply with a NATO ultimatum to end their siege or face air strikes.

U.N. officials reported large weapons convoys moving away from the Bosnian capital, an apparent effort by the Serbian rebels to comply with a week-old NATO order to withdraw or surrender all heavy weapons within a 12-mile radius of the capital by 1 a.m. Monday, Sarajevo time.

“It is a very heartening sign,” said Col. Bill Aikman, spokesman for the U.N. Protection Force in Bosnia. “Clearly, there’s a major withdrawal going on.”

Since NATO issued its ultimatum, fewer than three dozen of the Serbs’ hundreds of heavy artillery pieces had been removed before Thursday.

But U.N. observers reported the dramatic increase in compliance efforts after Bosnian Serb leader Radovan Karadzic met with a senior Russian envoy and announced that his nationalist forces will meet the NATO demand.

The envoy, Vitaly Churkin, conveyed to Karadzic a promise from Russian President Boris N. Yeltsin to contribute Russian soldiers to any new peacekeeping duties in Sarajevo if the Serbs would withdraw their heavy weapons from around the city, and urged them to turn over their artillery to U.N. forces “without delay.” The two men met in Pale, the Bosnian Serb stronghold southeast of Sarajevo.

Churkin said after the talks that the Serbs had agreed to withdraw their weapons. It was not clear whether that pledge resulted from the Russian offer or the looming threat of NATO attacks, but Yeltsin’s government claimed credit.

Yeltsin’s spokesman, Vyacheslav Kostikov, said in Moscow that the Russian offer and the positive response of the Serbs “make the NATO bombardments groundless.”

He told Russia’s Interfax news agency that Yeltsin’s plan “provides an opportunity to avoid an international conflict which could come about if the threat of air strikes materialized.”

Churkin, speaking on Russian television Thursday night, said he is certain the Serbs will withdraw fully from Sarajevo. He said the NATO ultimatum should be canceled.

“There will be no need for air strikes in Bosnia because there will be no objects to bomb,” he said.

Russian leaders have consistently opposed NATO air attacks and complained about not being consulted before last week’s ultimatum.

The United Nations’ Aikman declined to specify what weapons were sighted in the evacuating convoys. Nor would he say where observers believed the arms were being taken.

But he said that at the current pace, the Serb rebels could complete withdrawal from the exclusion zone within 36 hours--well ahead of the deadline set by NATO.

In Washington, President Clinton said NATO is determined to force compliance with its ultimatum, but he expressed hope that the crisis is easing. “I hope the air strikes will not be necessary, and they will not occur if the Serbs will comply,” Clinton told reporters.

And U.S. officials reacted cautiously to Yeltsin’s offer of troops for Sarajevo.

The United States has frequently tried to enlist Russian support to show solidarity between the world’s major nuclear powers. However, most Russians are far more sympathetic to the Serbs, with whom they share ethnic and religious backgrounds, than to the rest of the international community. So the presence of Russian troops could complicate NATO’s tough talk to the Serbs.

Meanwhile, NATO defense ministers agreed to meet at Aviano air base in Italy on Sunday, just before the alliance deadline. The base would be an important one if air strikes were ordered.

Defense Secretary William J. Perry will attend, meeting with the defense ministers of Britain, France, the Netherlands and Italy and with Gen. George Joulwan, the NATO commander, and Adm. Jeremy Boorda, head of the NATO air armada.

Perry will be accompanied by Gen. John Shalikashvili, chairman of the Joint Chiefs of Staff.

The U.N. reports of Serbian efforts to comply with the ultimatum came amid accusations by the Muslim-led Bosnian government that the rebels have been burying heavy weaponry on Mt. Trebevic, the Serb-held high ground at the southeastern edge of the city center.

Vice President Ejup Ganic told reporters that the Bosnian Serbs were “digging holes.”

“They’re trying to defuse the deadline,” Ganic alleged.

The Bosnian government has made no secret of its eagerness for Western military intervention to drive Serb forces back from the gun emplacements that surround the capital. Prime Minister Haris Silajdzic has said NATO action would provide “a balance of force” that would lead to liberation of Sarajevo and re-establishment of government control over a considerable swath of central Bosnia.

Bosnian Serbs loyal to the Belgrade government in the rump Yugoslavia have conquered and occupied 70% of Bosnia since taking up arms against this republic’s 1992 vote for independence.

Bosnian Serb military commanders had vowed to defy the NATO ultimatum, claiming withdrawal would be tantamount to “capitulation.”

And in a possible sign of internal conflicts about how to respond to the West’s ultimatum, a senior Bosnian Serb officer in an interview published Thursday reiterated threats to take foreign aid workers and journalists hostage in retaliation for any air strikes.

The rebel posture changed, at least publicly, after the Karadzic-Churkin meeting.

The U.N. reports of departing Serb convoys came as mobs of Sarajevans returned to the streets, reveling in the relative serenity that has followed the ultimatum and the first cease-fire of the war to last more than a few hours.

As the countdown to Monday’s deadline continued, even as NATO fighter jets screeched over the city in ear-splitting acts of intimidation, the public mood seemed more cynical than anticipatory.

Most people are so consumed by the daily shortages of food, water and electricity that few are concentrating on the pronouncements of the West, said Haris Pasovic, head of a theater troupe.

“Hoping too much is not good for our stomachs,” he said, alluding to earlier Western threats of force that were not followed through. “People don’t want to be betrayed anymore.”

In packed streets, children sledded in fresh snow, women marched out to get jugs of water, and dozens packed the few remaining cafes for sugarless Turkish coffee.

Some, like Selma Rizvic, claimed to be winning the fight for normalcy and dignity among the horrors. “The problem isn’t that we’re hungry,” said the 26-year-old computer graphics artist. “The problem is that we know what it is like to live normally. We’re not wild animals.”

Kirka reported from Sarajevo, Williams from Ancona, Italy. Times staff writers Richard Boudreaux in Moscow and Norman Kempster in Washington contributed to this article.