NATO said yesterday there would be no immediate air strikes against Yugoslav targets but maintained the threat of military action if Belgrade failed to comply fully with international demands for an end to the conflict in Kosovo.
"We have decided to maintain the activation order (ACTORD)," the NATO Secretary-General, Mr Javier Solana, said after a meeting of alliance ambassadors in Brussels.
"We have taken a decision not to act today," he said.
He said that security force numbers in Kosovo had returned to the levels they had been before the conflict began - one of the key demands of the international community on the Yugoslav President, Mr Slobodan Milosevic.
"Over the past 24 hours over 4,000 members of the [Serb] special police have been withdrawn from Kosovo. Police and military units based in Kosovo are moving back to their barracks with their heavy weapons," he said.
The activation order authorised NATO military commanders to launch a strike after 7 p.m. yesterday if Yugoslavia was judged to be defying the international community.
The pull-back was welcomed by Britain, the US and Germany but Washington and London were quick to warn Belgrade that NATO pressure would continue until all UN demands were met.
"This is a chance, not a guarantee," President Clinton said at a White House reception.
He warned Mr Milosevic that "he must stay in compliance".
"We should be under no illusion, there is still a lot of hard road to walk," Mr Clinton said.
Britain's Foreign Secretary, Mr Robin Cook, said he welcomed "NATO's decision to maintain its readiness to act.
"NATO has not and will not lower its guard: the planes will stay on the runway," Mr Cook said.
Reporters travelling the length and breadth of Kosovo found no police checkpoints or security presence on major roads aside from occasional regular police on patrol.
The US special envoy, Mr Richard Holbrooke, who negotiated basic withdrawal conditions with Mr Milosevic, said the Serbs' performance so far looked good.
"Frankly, I hate to use the `O' word in the Balkans, but there is reason . . . for some more optimism than we've had in the past," Mr Holbrooke told Cable News Network (CNN) in Washington.
"Serb security forces are pulling out. The international verification regime is pouring in . . . The [Serbs] have allowed Kosovo, which they have always said was their private backyard, to become an international issue and once the international community is in there, it is going to make a huge difference in stabilising the situation."
There has been some concern that undisciplined ethnic Albanian separatist guerrillas, whose quest for independence was crushed by Belgrade's firepower this summer, might occupy vacated land, inviting Serbian counter-attack.
But the Kosovo Diplomatic Observers Mission (KDOM) reported no serious problems in the waning hours before NATO's deadline.
Mr Shaun Byrnes, head of KDOM's American contingent, said KDOM knew of only three company-size units of Yugoslav military still deployed outside garrisons - in the south-west Stimlje Suva Reka area, outside the airfield of the provincial capital Pristina, and south of the central town of Klina.
KDOM teams have negotiated region-by-region pacts with guerrilla units under which they promised not to advance on the heels of retreating Serbs, block roads or take any other military action, a Western diplomat in the region said.
Some 2,000 international monitors will enter Kosovo soon with Serbian approval to verify demilitarisation, help refugees resettle safely and foster a climate for talks on self-government for Kosovo.
Meanwhile, President Milosevic sacked Mr Jovica Stanisic, his state security chief and long-time right-hand man, reports from official media revealed yesterday.
Mr Stanisic's exit followed independent media reports that he had opposed recent repressive policies, including a fierce military crackdown in Kosovo.