NATO and the United Nations tried today to bolster confidence in their Kosovo mission, which has been shaken by the massacre of 14 Serbian farmers in what officials called a deliberate attempt to wreck peacekeeping efforts.

The Serb-led Yugoslav government demanded an urgent meeting of the U.N. Security Council to discuss ways to stop ethnic violence in Kosovo and insisted that Yugoslav forces be allowed back into the Serbian province, the state-run Tanjug news agency reported Saturday. Serbia is the dominant republic of the Yugoslav federation.

Kosovo's U.N. administrator, Bernard Kouchner of France, and the head of the NATO-led peacekeepers, British Lt. Gen. Mike Jackson, said the killings Friday were aimed at their mission. "The murderers sought to stop us. We must not permit that," said Koucher. "Our mission must go on."

The killing of the 14 Serbs in a field near the central Kosovo village of Gracko was the bloodiest incident in a wave of anti-Serb violence that has jeopardized the U.N. goal of bringing about a peaceful, multiethnic Kosovo. Kosovo's Serbs have been targeted for killings, house burnings and other violence in what are believed to be revenge attacks by some of more than 700,000 returning ethnic Albanian refugees who were driven from Kosovo by Serb-led security forces.

An estimated 10,000 ethnic Albanians were killed by government troops and police before and during the 78-day NATO bombing campaign that eventually forced Belgrade to accept a peace plan and pull its forces out of Kosovo.