Relief Officials Assail Bosnia Serbs Over Blockade : Balkans: The Sarajevo government suspends aid deliveries within capital in gesture of solidarity with besieged eastern enclaves.

Humanitarian relief officials condemned Bosnian Serbs on Friday for blocking lifesaving food and medicine from Muslim Slav communities in eastern Bosnia and criticized the Sarajevo leadership for “grandstanding” on the issue.

The action came even as U.N. officials threatened to withdraw peacekeepers from Croatia and a new American special envoy traveled to Moscow to consult with Russian leaders about ways to bring peace to Bosnia-Herzegovina.

Sarajevo city officials announced that they were suspending delivery of relief goods in the besieged capital in a gesture of solidarity with those in isolated eastern enclaves deprived of aid for months by Serb militants trying to starve them out of their homes.

The self-imposed hunger strike in a city itself enduring severe hardship illustrated the desperate extremes to which the Bosnian leadership has been pushed in its 11-month-old effort to defend the country against a brutal ethnic partitioning.

In response to the aid suspension, U.N. High Commissioner for Refugees Sadako Ogata sent a protest letter to Bosnian Serb leader Radovan Karadzic, reminding him of commitments to allow free passage of humanitarian convoys through the vast Bosnian territory his gunmen control.

More than 1,000 tons of relief goods now sit in Sarajevo warehouses--enough to feed the city’s 380,000 holdouts for at least five days, said Peter Kessler, of the U.N. agency’s Zagreb office. “We know how frustrated they are and understand their frustration, but we are risking our lives to get aid in to this region and it is not getting to the people who need it,” Kessler said.

A spokeswoman at the agency’s Geneva headquarters was more critical of the Bosnian move, which some officials fear is being forced on the capital’s starving residents. “While the high commissioner understands the desperate concerns for the people in eastern enclaves, we don’t feel that this kind of grandstanding is very productive,” said spokeswoman Sylvana Foa.

A Western airlift into the Bosnian capital began last July to feed Sarajevo residents who refuse to be driven out of their homes by the daily artillery barrages unleashed by Serbian militants who have encircled the city with tanks and guns. The rebels, armed and instigated by Serbian nationalists in Belgrade, have embarked on a campaign to create an ethnically pure state within Bosnia for future annexation to the republic of Serbia.

Eleven months of siege, mass deportations, imprisonment, beatings, rapes and killings have been used by the Serbian militants to rid 70% of Bosnian territory of all but Serbs, who were 31% of the republic’s population before the rebellion began.

“We cannot wait for a political solution while people are dying, suffering, being expelled and subjected to all kinds of violence and harassment,” said Jose Maria Mendiluce, the U.N. agency’s special envoy to the former Yugoslav federation, promising to step up pressure on the warring factions to spare civilians from their bitter conflict. He vowed to push ahead with relief deliveries regardless of whether warring leaders gave their permission to pass.

Mendiluce estimated that up to 200,000 people are trapped by the Serbian stranglehold on Muslim pockets in eastern Bosnia.

He dismissed as “cynical” a claim by Karadzic forces that they had opened a humanitarian corridor to allow 6,000 starving and terrorized Muslims to flee for their lives to the government-held city of Tuzla.

The U.N. aid agency, “in its 41-year history has never been in a situation so radicalized, so polarized, with such a high level of hatred and lack of humanitarian behavior,” Mendiluce told journalists in Belgrade.

Conditions are reported to be the worst in the few remaining Muslim communities along the Serbian border, where Bosnian Serb extremists backed by paramilitary gangs from Belgrade began their “ethnic cleansing” of Bosnia’s Muslims last March. At least 20,000 people--mostly Muslim civilians--are known to have been killed in the siege of Bosnia, and government leaders contend the actual death toll is probably 10 times higher, if those missing and presumed dead are included.

Meantime, in New York, Secretary General Boutros Boutros-Ghali warned Friday the United Nations might have to withdraw its 12,750 peacekeepers from Croatia unless an agreement stifles the battling between Croats and Serbs.

In a report on the civil war in the former Yugoslav republics, he proposed that the Security Council extend the peacekeeping mandate in Croatia, due to end on Feb. 21, for only one month while an attempt is made to work out a settlement.

He said he had asked the two diplomats who are trying to mediate a Bosnian peace--Cyrus R. Vance, the former U.S. secretary of state and special U.N. envoy, and Lord Owen, the European Community negotiator--to take on the same role for Croatia as well. The Council is expected to approve the one-month extension.

While acknowledging that the peacekeepers had managed to lay down no more than a fitful peace for most of the year, the secretary general displayed a good deal of acrimony as he denounced the Croats for launching an offensive against Serbian positions on Jan. 22. The Serbs then broke into U.N. storage areas to take back their heavy weapons.

Boutros-Ghali said it has proven impossible to bridge the gap between the Croatian government and the Serbian minority that insists on the right to secede and declare itself “the Republic of Serb Krajina.” He said that “a sound basis will not exist” for keeping peacekeepers in Croatia unless this distrust is dissipated.

In his report, he said there were now 12,750 peacekeepers in Croatia, 9,000 in Bosnia, 200 in Macedonia and 1,000 people serving as observers throughout the former Yugoslav republics. In all, U.N. casualties now total 26 dead and 337 wounded.

In Moscow, Reginald Bartholomew, the new American special envoy to the former Yugoslav republics, arrived Friday to seek renewed support for Western peace efforts and U.N. sanctions against Serbia. He is expected to meet today with Russian Foreign Minister Andrei Kozyrev, legislative leaders and Deputy Foreign Minister Vitaly Churkin, the Kremlin’s special envoy to the conflict.

Under pressure from opposition lawmakers to side with Russia’s fellow Orthodox Slavs in Serbia, Russian President Boris N. Yeltsin last month criticized American policy toward the former Yugoslav federation as too rigid and called for more peace efforts. But he has continued to support sanctions. His cooperation is crucial for the West because Russia has veto power in the Security Council and carries influence with the Serbs.

Kozyrev endorses the American peace initiative but expresses more explicit support for the Vance-Owen plan, which he said “largely coincides with Russia’s position” and offers “real chances for the solution of the conflict.”

Under questioning Friday by lawmakers in the Supreme Soviet, Kozyrev defended Moscow’s support for sanctions against Serbia but warned that Russia will seek to apply them against Croatia, “if Croatia continues along that road of wrecking agreements by unleashing murderous actions” against the country’s Serb minority.

Times special correspondent Laura Silber in Belgrade and Times staff writers Stanley Meisler at the United Nations and Richard Boudreaux in Moscow contributed to this report.