BRUSSELS, Belgium -- For the second time in two weeks, NATO leaders failed yesterday to agree on a formula for providing military support for relief shipments to the strife-torn former Yugoslav republic of Bosnia-Herzegovina.
Alliance ambassadors from the United States and the 15 other member nations considered a proposal to commit 6,000 troops to the relief effort, but they deferred action until after the three-day international conference on Yugoslavia that begins today in London.
Elsewhere on the eve of the London conference:
* Lord Carrington, a British diplomat and former NATO secretary-general, resigned after a frustrating 11 months as chairman of the European Community's peace conference on Yugoslavia.
* The U.N. General Assembly adopted a non-binding resolution urging the Security Council to take tougher action against Serbia, the former Yugoslav republic that is widely regarded as the aggressor in the recent violence. Many Muslim nations, expressing support for the Muslim plurality in Bosnia, had urged tougher action.
* Serbs ringing the Bosnian capital of Sarajevo blasted the presidential palace and military headquarters with rockets and mortar fire. Authorities reported 93 people killed in Bosnia on Monday in one of the bloodiest days since the nation's Muslims and Croats declared independence from Serbia in February.
NATO's failure to act yesterday reflected both the enormous potential dangers of conducting military activities in the midst of the Bosnian civil war and the concern felt by some NATO members that the alliance should not act before the London conference.
On Aug. 14, one day after the U.N. Security Council authorized the use of force if necessary to protect relief shipments to Bosnia, NATO ambassadors rejected a plan by its military staff to dispatch as many as 100,000 troops to secure a land corridor from the Adriatic Sea to Sarajevo, which is about 100 miles inland.
The staff then developed a much more modest option: the assignment of 6,000 troops to accompany relief convoys. Under the "light option," as the staff called it, the 6,000 NATO troops would operate "under U.N. command and rules of engagement."
But NATO ambassadors yesterday deferred action on this approach as well. "It was decided to return to the subject after the London conference," a NATO spokesman said. Other sources said Germany and France were particularly reluctant to act.
Lord Carrington's resignation as chairman of the EC's Yugoslav peace conference will deprive the international peacemaking effort of the diplomat who once oversaw the difficult negotiations leading to Southern Rhodesia's independence as the nation of Zimbabwe.
"I have decided that after a year's intensive association with the peace conference I can no longer devote to it the full-time effort which will be necessary and will extend over a considerable period," said the 73-year-old diplomat.