Diplomats Report All-Out Serb Offensive in East Bosnia : Balkans: Drive for conquest has reportedly been spurred by absence of any credible deterrent.

In the absence of any credible threat to stop them, Serbian rebels in Bosnia-Herzegovina are waging an all-out drive to conquer the last few non-Serbian communities in eastern Bosnia, diplomats and aid workers warned Wednesday.

A convoy of lifesaving aid has been held up by Serbian gunmen at the Bosnian border for the past week, less than 20 miles from the beleaguered city of Srebrenica, which is being pounded by rebel tanks, artillery and aircraft.

One of only four non-Serbian pockets remaining in the republic’s ravaged east, Srebrenica has become a gruesome death trap where starving and wounded Muslim Slav refugees from other vanquished enclaves are succumbing on the snowy streets after their futile trek in search of food and shelter.

Field workers for the Office of the U.N. High Commissioner for Refugees describe the scene in Srebrenica as “appalling,” according to agency spokeswoman Lyndall Sachs.

“Conditions are deteriorating very rapidly,” she said, relaying reports from refugee agency staff on the scene of intensifying bombardment. “We’ve been told that people are so desperate they are willing to kill for what they can get from the airdrops” of food and medicine parachuted from U.S. planes each night.

Some political observers accuse mediators Cyrus R. Vance, representing the United Nations, and Lord Owen, representing the European Community, of turning their backs on vulnerable communities such as Srebrenica to speed the ethnic partition of Bosnia that is necessary for the success of their proposed peace plan.

Milos Vasic, military affairs editor for the respected Belgrade weekly Vreme, contends that there is no other explanation for the United Nations’ reluctance to mount an airlift to the Bosnian government stronghold of Tuzla from which the dying communities could be supplied.

“Someone is deliberately trying to avoid helping Tuzla, even though there are as many people in danger there as in Sarajevo and logistically it is easier to supply those critical areas of eastern Bosnia from there,” Vasic said, noting that Tuzla has a sizable and intact airport through which a new lifeline could be established.

Nearly 700,000 Bosnians from various ethnic groups are living in the archipelago of communities still loyal to the Sarajevo government that extends southeast from Tuzla to Srebrenica, Zepa and Gorazde.

Although there was no indication the Serbs would relent and let aid through to Srebrenica, the U.N. refugee agency was informed late in the day that convoys destined for Sarajevo, Gorazde and Tuzla would be allowed to proceed.

Sachs said trucks set off from the Yugoslav-Bosnian border for Sarajevo and Gorazde before sunset but that the Tuzla-bound convoy was ordered to wait for daybreak.

However, state-run TV Serbia reported that none of the convoys would be permitted to unload relief goods unless the refugee agency promised to “evacuate” Serbs still living in the pro-government enclaves.

Most of the Serbs still in Sarajevo and Tuzla are believed to support a united Bosnia. The Sarajevo leadership denies any are being detained against their will, as charged by Serbian rebel leaders.

An official of the refugee agency said it fears that the convoys headed for Sarajevo and Gorazde could become pawns in a protracted standoff with the Bosnian Serb authorities seeking its help with “ethnic cleansing,” which has already displaced nearly half of Bosnia’s 4.4 million people.

Diplomats expressed surprise at the Bosnian Serbs’ aggression at a time when most Western countries are threatening to tighten sanctions against all Balkan Serbs for waging war on civilians.

Vance and Owen resumed talks with the warring factions in New York on Wednesday amid threats by Washington and other powers to impose even more severe punishment on the Serbs unless they stand down.

The U.N. Security Council ordered a halt to all trade and assistance to Belgrade last May in an effort to pressure the nationalist regime ruling the remains of Yugoslavia to cease arming and instigating the Bosnian Serbs.

A complete cutoff of transport and communications is now being threatened unless Serbian President Slobodan Milosevic, widely accused of masterminding the nearly 2-year-old Balkan war, uses his influence with Bosnian proxies to end the sieges that have left at least 150,000 dead or missing.

Despite the threat of total isolation if the Bosnian Serbs continue to reject the Vance-Owen peace plan, Milosevic last week refused to endorse the diplomatic proposal.

On the contrary, the Serbs have since stiffened their resolve to block aid to the communities in their gun sights.

One Belgrade-based envoy said he fears the latest offensive and thwarting of relief efforts suggest that the Serbs have determined that the international community is giving no serious consideration to effective intervention.

“The Serbs have learned they can get away with murder,” the diplomat said.

Bosnian Death Trap

In the streets of Srebrenica, starving and wounded refugees from other vanquished enclaves are succumbing for lack of food or shelter.