The agreement, which was signed after three days of intense negotiations, gives Moscow control of a 3,600-strong Russian force, although they will not be in a separate Russian sector, as Moscow had been demanding.

Under the terms of the deal, the Russian troops are expected to patrol three main areas: the northern part of the US-controlled sector, the north-western part of a sector under German control and a small area of a French-controlled sector in the north.

The airport at Pristina will be run jointly, with the Russians in charge of services on the ground and Nato controlling flights.

Mr Cohen and Russian Defence Minister Igor Sergeyev signed the deal in Helsinki late on Friday.

US President Bill Clinton, who is due to meet Russian President Boris Yeltsin on Sunday in Cologne, said that he supported the deal and that the deployment of Russian forces would reassure the Serb minority in Kosovo.

The breakthrough has also been welcomed at the G8 summit, attended by the seven major industrialised countries and Russia.

Serb withdrawal on target

President Clinton: "It will help to send a message to both sides"

Yugoslav troops succeeded in pulling out of central Kosovo by the agreed deadline of midnight on Friday, and Nato said a full withdrawal from the province could be completed ahead of schedule.

The alliance said three quarters of the estimated original 40,000 Serb ground troops had left Kosovo.

General Sir Mike Jackson, the Commander of K-For, said he hoped that the withdrawal would be completed 24 hours ahead of the scheduled time of Sunday at midnight.

The UN agency is stepping up attempts to warn Kosovo Albanians that it was not safe to go home until mines are cleared and international organisations give them the green light.