The paramilitary group is led by Zeljko Raznjatovic, known as Arkan, who has been charged with war crimes in Bosnia and has been accused of attacking ethnic Albanians in Kosovo.

Yet for his part, Mr. Ivanovic says he cannot control the Serbs who attack ethnic Albanians, saying it is too dangerous for him to take the side of Albanians.

The NATO air campaign, intended to the capability of Serb forces to attack ethnic Albanians had apparently not done so in the first two nights, military experts said.

Refugees talked of seeing their Serbian neighbors join marauding Government forces to attack ethnic Albanians, then loot and burn their homes.

His gang, "Arkan's Tigers," has been accused of attacking ethnic Albanians in Kosovo.

But he did not agree to one key demand: the withdrawal of Serbian security forces accused of attacking ethnic Albanians in the province.

The group was also accused of attacking Albanians, Croats, Hungarians, Roma people, as well as spreading antisemitic propaganda and preaching hate.

But the allies' main weapon of choice against ground troops attacking ethnic Albanians in Kosovo has done little but fly reconnaissance circles in the air.

Serbian forces, for example, had become accustomed to leaving their hiding places soon after allied planes had passed, trying to take advantage of gaps in the allied patrols to attack ethnic Albanians.

NATO acknowledged today that an allied warplane had mistakenly bombed a civilian vehicle in southern Kosovo on Wednesday while trying to stop Serbian forces from attacking ethnic Albanians.