At Russian Urging, Serbs Agree to Let Airport Open : Bosnia: Relief flights will be allowed into Tuzla. Rebel leader makes announcement during Moscow visit.

At Russia’s urging, Bosnian Serb leader Radovan Karadzic capitulated in a major standoff with the West by agreeing Tuesday to allow U.N. forces to reopen an airport in northern Bosnia-Herzegovina for humanitarian relief flights.

The announcement by Karadzic--during a Moscow visit in which he had sought moral support in the Balkan conflict--clearly indicated that there are limits to the political capital Russia is willing to spend on its internationally condemned Serbian allies who are waging war against other Slavs.

Karadzic’s concession in allowing the airport to reopen was the second time in less than two weeks that Russia has intervened to resolve an impasse in the Balkan crisis. It was at Moscow’s insistence that Karadzic complied with a NATO ultimatum to withdraw or surrender heavy weapons around Sarajevo by Feb. 21.

The Bosnian Serb leader flew to Moscow on Monday, only hours after North Atlantic Treaty Organization forces shot down four planes that Karadzic loyalists had used to fly combat missions in violation of a U.N. “no-fly” order imposed over Bosnia.

NATO’s first-ever use of force may have changed the course of the Bosnian conflict by showing combatants there that the West is committed to resolving the war that has racked the former Yugoslav republic for 23 months.

Instead of getting an endorsement of the hard-line control that Serbian rebels have maintained over the airport, Karadzic emerged from talks with Russian Foreign Minister Andrei V. Kozyrev to announce that a U.N.-operated humanitarian airlift to the mostly Muslim Tuzla region will begin soon.

Officials at U.N. headquarters in New York last week set next Monday as the deadline for opening the strategic airport to funnel food and other relief goods to those in need in the largest of Bosnian government-held regions. At least 800,000 people live in the Tuzla pocket, hemmed in by a Serbian rebel siege on three sides and by fighting between Muslims and Croats to the south.

At a NATO summit in January, the Western alliance threatened to use force, if necessary, to establish an airlift to Tuzla and to ensure safe rotation of a U.N. peacekeeping contingent in another besieged Muslim enclave, Srebrenica.

Karadzic and his military chieftains had conceded the troop rotation issue. But they refused to give assurances that an airlift, like the one servicing Sarajevo, would be allowed to operate out of Tuzla. The rebels contended that the airport, although under U.N. administration, would be used to deliver weapons to the Bosnian government.

In a statement released after Karadzic and Kozyrev met, the Russian Foreign Ministry announced that the Tuzla airlift will begin “in the near future” and that Russian observers will be stationed at the site to ensure that the operation remains humanitarian.

The announcement suggested that the opening may not occur definitively next Monday.

By pushing back the start-up and insisting on some Russian presence at the airport, Moscow provided a face-saving retreat for the Bosnian Serbs. Russians share the Orthodox faith with the Serbs but have had to walk a narrow path between their traditional allies and the Western countries with which they hope to establish stronger political and economic ties in the post-Cold War era.

Karadzic’s sudden visit to Moscow consolidated a strategy under which Kozyrev has been deployed to tackle the Serbian side of the Balkan conflict while leaving Washington to deal with the Muslims and Croats.

By compelling Karadzic to give up rebel opposition to the relief mission, Moscow showed itself to be more aligned with the international community’s quest for peace in the Balkans than behind the Serbian nationalists whose deadly land-grab has drawn widespread condemnation.

Andrei V. Kortunov, a foreign policy expert at Moscow’s U.S.A.-Canada Institute, said Russia has established a “balanced position, trying not to corner the Serbs,” and has found that approach “more promising than NATO’s rigid position.”

“It seems to me that Russian diplomacy has somewhat unexpectedly been a serious success,” Kortunov said. He argued that backing the Serbs into a corner could prompt them to behave “even more irrationally and aggressively.”

Russia’s role in the crisis remains suspect among supporters of the Bosnian government, however, because of the obvious backing Russian troops have given the rebels.

When 400 Russian peacekeepers arrived in Serb-held areas around Sarajevo on the eve of the NATO ultimatum, they soaked up the cheers and plum brandy offered by jubilant Serbian civilians and flashed the three-fingered sign of solidarity with their Orthodox brothers. The reception prompted Bosnia’s Muslim president, Alija Izetbegovic, to appeal to the United Nations not to send more Russian soldiers to his republic.

Moscow’s special envoy for the Balkan crisis, Deputy Foreign Minister Vitaly S. Churkin, said during his latest visit to Sarajevo that the Russians were sent to provide “a degree of psychological comfort” for Serbs once their heavy artillery was withdrawn.

Some of the Russian soldiers, however, told journalists that they had been sent to protect the Serbs.

In Washington, U.S. and British officials went out of their way to praise Russian intervention.

“If they can be influential with the Serbs in bringing about a settlement that’ll be acceptable to the Muslims and the Croatians, then I think we’d welcome that kind of help,” Secretary of State Warren Christopher said Tuesday.

President Clinton, during a brief news conference Tuesday with British Prime Minister John Major, said he was “encouraged” by the “willingness of the Russians to work with us and others trying to bring the Serbs into a final peace agreement.”

Major made a similar statement and announced plans to send a U.S.-British civil engineering team to Sarajevo to begin work on repairing roads, bridges and other facilities that have been damaged by nearly two years of war.

The team will involve “engineers from the U.K. and the U.S. going there to look at ways to get gas service, water service, electrical service back, to restore some of the infrastructures--roads, bridges,” White House Press Secretary Dee Dee Myers said.

Efron reported from Moscow and Williams from Vienna. Times staff writer David Lauter in Washington contributed to this report.