The United States and its allies gave a detailed peace plan to the European Union's Balkans envoy yesterday so he can explain to Yugoslav President Slobodan Milosevic exactly what he must do to meet NATO's conditions for halting its bombing campaign and to resolve the Kosovo crisis.

Italian Foreign Minister Lamberto Dini said after talks with Secretary of State Madeleine K. Albright that among NATO's demands is that Milosevic provide a precise schedule for the withdrawal of Serb-led Yugoslav forces from Kosovo "in a short period of time." A U.S. official said there would have to be a "visible and verifiable" pullout over about a week for a cease-fire to take effect.

The EU envoy, Finnish President Martti Ahtisaari, is expected to spell out NATO's terms when he meets with Milosevic in Belgrade today; it will be the first official contact between a Western official and Milosevic since NATO airstrikes began March 24.

Ahtisaari will be accompanied by Russian envoy Viktor Chernomyrdin, whose mediation efforts have foundered in the eyes of Western governments because of Moscow's refusal to back NATO's key demands that NATO troops form the core of any international peacekeeping force in Kosovo and that all Belgrade government forces withdraw from the province to encourage more than 800,000 ethnic Albanian refugees to return to their homes there.

Senior U.S. and NATO officials described the Ahtisaari mission as a fateful moment in the quest for a settlement to the crisis over Kosovo, a province of Serbia, Yugoslavia's dominant republic. If Ahtisaari fails to persuade Milosevic to accept the alliance's terms, the officials predicted that diplomatic efforts that have been building over the past two weeks to end the conflict would collapse.

NATO warplanes pounded Yugoslav sites for the 70th day, flying nearly 800 sorties that included 319 attacks on military targets, plus strikes in and around Belgrade. Yugoslav news broadcasts said that Gen. Ljubisa Velichkovic, the deputy air force chief of staff, was killed while visiting troops; he was identified as the highest-ranking Yugoslav casualty since the bombing began.

Ahtisaari will have relatively little latitude to negotiate in his meeting with Milosevic, State Department sources said. While the Finnish leader can discuss cease-fire conditions with Milosovic, they said, the composition of the international security force for Kosovo will be primarily a subject of Western talks with Moscow, not Belgrade. "Deciding what command and control, that's not Slobo's problem," a Clinton administration official said. "That's not something to discuss with him."

Despite Ahtisaari's professed reluctance to go to Belgrade while there are lingering disagreements between Russia and NATO, he was urged to do so by allied governments who want to make sure Milosevic is fully aware of their conditions for ending the conflict. Senior NATO diplomats said they have doubts that Chernomyrdin, during his four previous visits to Belgrade, was properly conveying the allied position.

At NATO military headquarters near Mons, Belgium, meanwhile, representatives of the 19 NATO member states and a dozen other countries discussed contributions of troops and equipment to the projected peacekeeping contingent that is now expected to number 50,000 soldiers. That force would be sent into Kosovo only when Milosevic withdraws his troops, and it is not designed -- at least for now -- to serve as the vanguard of a ground invasion to expel the estimated 40,000 Yugoslav troops and Serbian police now hunkered down across the province.

The NATO plan was given to Ahtisaari by Deputy Secretary of State Strobe Talbott during a meeting today with Chernomyrdin near Bonn. U.S. and NATO sources said it reaffirms the alliance's five conditions for halting the bombing and prescribes a timetable, verification methods and the composition of a Kosovo peacekeeping force.

The NATO terms call for an end to violence and repression against Kosovo's ethnic Albanian population; the withdrawal of all Yugoslav forces; the introduction of an international security presence with NATO troops at its core; the safe return of all refugees to their homes; and the start of a political process that would restore self-government in Kosovo, where ethnic Albanians outnumbered Serbs nine to one before most were driven from the their homes.

After the meeting, Ahtisaari said although the envoys had not agreed "100 percent . . . it's fair to say at this stage we're prepared to go and see if the Yugoslav government is ready to accept" the framework they discussed.

In a letter to Germany received yesterday, Milosevic reiterated his acceptance of the principles of a Kosovo settlement laid down by the Group of Seven industrial democracies and Russia. These points largely reaffirm NATO's conditions but do not include its insistence that it command any peacekeeping force and that all Yugoslav forces leave Kosovo, at least temporarily.

Russia has demanded that the security force be placed under U.N. auspices and that troops from NATO countries leading the bombing campaign -- such as the United States, Britain and France -- must not be part of the peacekeeping contingent. Moscow has also contended that Belgrade should not be required to forsake its sovereignty over Kosovo by withdrawing its security forces.

On the latter issue, alliance diplomats said the gap has narrowed in recent days. NATO now says that a few hundred Yugoslav troops might be allowed into Kosovo to conduct border patrols and guard religious sites. After insisting that Yugoslavia should be allowed to keep up to 20,000 troops in Kosovo, Chernomyrdin now says that Russia would agree to as few as 800.

Yugoslav political and military leaders sought to press ahead with a diplomatic offensive emphasizing their desire to compromise. Gen. Nebojsa Pavkovic, commander of Yugoslavia's Third Army in Kosovo, was quoted as saying that a political solution could soon be achieved once the "crucial diplomatic battle" over the withdrawal of soldiers and police from Kosovo and the composition of the peacekeeping force was settled. But Pavkovic reiterated Belgrade's demand that it be allowed to maintain "peacetime" military levels in Kosovo, which have ranged up to 11,000 troops and 25,000 policemen.

Drozdiak reported from Brussels, Mufson from Washington. Correspondent Daniel Williams in Belgrade contributed to this report.