BELGRADE, Yugoslavia (AP) _ After a marathon all-night session, U.S. envoy Richard Holbrooke returned for another round of talks today to try to persuade Yugoslavia's leader to end his crackdown in Kosovo.

The last-ditch negotiations came as U.S. warplanes were shifted closer to Yugoslavia for possible NATO airstrikes and dozens of foreign diplomats were being evacuated from Yugoslavia.

Holbrooke returned to his hotel just before dawn today, following an 11-hour meeting with President Slobodan Milosevic and three hours on the telephone with Secretary of State Madeleine Albright and National Security Adviser Sandy Berger.

Holbrooke described his meeting with Milosevic as ``intense, indeed, and at times very heated.'' He said the standoff between NATO and the Yugoslav president ``can only be called an emergency.''

The two men resumed talks later in the morning.

NATO officials meeting in Brussels, Belgium, today are expected to issue an ``activation order'' for NATO airstrikes against Yugoslavia unless diplomacy produces a breakthrough. The start of the meeting was delayed this morning until later in the day, but no reason was given.

Foreign presence in Yugoslavia was being reduced in anticipation of NATO action.

The international team of U.S., Russian and other diplomats observing events in Kosovo over the past months was to drive to neighboring Macedonia later today. Sources at the U.S. Embassy said all but 12 people would be evacuated from Belgrade to Budapest, Hungary.

The Germans were expected to do the same, while British embassy staff was waiting for the outcome of the Holbrooke-Milosevic talks.

The Americans and Europeans are demanding that Milosevic halt the crackdown he launched Feb. 28 against the separatist Kosovo Liberation Army.

The major obstacle appears to be Holbrooke's demand that Milosevic agree to an expanded international monitoring mission to verify compliance with demands of the U.N. Security Council.

Those demands include an immediate cease-fire, a withdrawal of special troops in the province, allowing refugees to return home and beginning talks with ethnic Albanians on Kosovo's future.

Kosovo is a province of Serbia, the main republic of Yugoslavia. About 90 percent of its 2 million people are ethnic Albanian, and most of them want independence or substantial self-rule.

Milosevic's crackdown on the KLA has killed hundreds, and forced at least 270,000 ethnic Albanians to flee their homes. There was sporadic gunfire and smoke Sunday in the ethnic Albanian village of Makrmalj, 20 miles west of Pristina, but Serb police blocked journalists from the area.

Rebels claimed the activity was part of a police operation.

The Pentagon is continuing military preparations if Holbrooke's mission fails. Six U.S. B-52 bombers arrived in Britain on Sunday and a contingent of A-10 anti-tank planes flew from Germany to Italy.

French Defense Minister Alain Richard said France would provide about 40 planes for possible air strikes. He told France-2 television that air strikes could last ``several days.''

The Cabinet of outgoing German Chancellor Helmut Kohl is also to formally back the possible airstrikes.

Meanwhile, Sen. John McCain, R-Ariz., warned that Americans could be killed in the bombing raids. ``There will be significant jeopardy there because the Serbians have a very good defense system,'' the former Navy pilot said on ``Fox News Sunday.''

The Romanian government agreed to let NATO use its airspace in an emergency. Australia today warned its citizens to immediately leave Yugoslavia.

Yugoslavia's defense minister, Pavle Bulatovic, warned neighboring countries Sunday that a NATO attack could turn the Balkans into ``a powder keg.''

Russian Foreign Minister Igor Ivanov expressed his country's opposition Sunday to any NATO strike, saying they could lead to ``international chaos.''

Efforts to end the seven-month crisis intensified following allegations that Serb police massacred scores of ethnic Albanian refugees. Concern is mounting that winter will bring a humanitarian disaster if thousands remain homeless by the first snowfall.

The United Nations has condemned recent massacres of ethnic Albanians, but has not endorsed airstrikes. The Clinton administration believes, however, it does not need a new U.N. resolution for the attacks.