The meeting on Thursday is likely to put extra pressure on Serbian President Slobodan Milosevic as he considers his position on the peace plan put to him by the EU and Russia.

Mr Clinton also announced the US would contribute 7,000 troops to the force deployed in Kosovo if Mr Milosevic accepts a peace agreement.

Mr Clinton said: "There is a clear choice before the Serbian leader.

"He can cut his losses now and accept the basic requirements of a just peace or he can continue to force military failure and economic ruin on his people.

"The outcome will be the same."

Russian and EU peace envoys made their first joint attempt on Wednesday to persuade Mr Milosevic to accept a peace plan for Kosovo.

They handed a peace plan to Mr Milosevic in Belgrade after settling last-minute differences over the proposals.

Freezing weather

Nato is preparing for a Kosovo peacekeeping force (KFOR) of 50,000, including 7,000 US troops, if current diplomatic efforts are successful.

But if they are not not, administration and military officials said Nato and Washington must begin at least making tentative plans to increase KFOR sharply for a possible ground war.

Only a few months remain before freezing weather comes again to southern Serbia's mountains.

President Clinton said 68 more US aircraft were to be deployed in the Balkans.

Mr Clinton also said that an extra 3,000 US troops, taking the total to 7,000, will be joining the peacekeeping force.

"Our European allies will provide the vast bulk of peacekeeping troops, but America will also contribute," he told cadets graduating from Colorado Springs Air Force Academy.

BBC Washington Correspondent Stephen Sackur: President Clinton is feeling under pressure

Recent polls have shown Americans generally would not support an invasion in which possibly hundreds of US troops could be killed.

But in the absence of any clear sign that President Milosevic is prepared to back down - and with the air campaign in its third month, Nato's options are becoming increasingly limited.

BBC Washington Correspondent Stephen Sackur said: "The air war is not working as fast as the White House and military officials would like it to be working.

"People believe in Washington that if the air war is not successful and Milosevic does not back down by the middle of June, then there will have to be serious preparation for a ground force to be deployed in Kosovo."