The NATO allies early today unanimously voted a green light for air strikes against Serb forces in Yugoslavia, giving the US envoy, Mr Richard Holbrooke, the big stick he had reportedly sought before going into further talks with President Slobodan Milosevic of Yugoslavia.
But the NATO Secretary General, Mr Javier Solana, said the vote provided a 96-hour delay, "from right now", before the strike order could be implemented.
Diplomats in Brussels said Mr Holbrooke told them that the Organisation for Security and Co-operation in Europe could deploy 2,000 observers in Kosovo. Mr Holbrooke, who flew to Brussels late on Monday night to brief the allies on his talks with Mr Milosevic, told them he foresaw an OSCE role in the verification of any commitment the Yugoslav leader made to abide by UN resolutions in Kosovo.
In addition, NATO might play a role in protecting the OSCE personnel on the ground, using planes and pilotless drones, the same sources said.
According to reports of progress Mr Holbrooke had made in his talks in Belgrade, Mr Milosevic would agree to make a "unilateral declaration" on autonomy for Kosovo and its 90 per cent ethnic Albanian population.
Meanwhile, a senior US official in Washington said Mr Milosevic has agreed to withdraw his troops from Kosovo as part of a deal to avert NATO air strikes.
"We have got his commitment on 1199," the official said, referring to a UN resolution calling for the pull-back of troops from the Serbian province.
The deal calls for a "crisp", or fast-paced, negotiating timescale, as well as strict verification of the withdrawal from the air and on the ground. "These are key," the official said.
But the official stressed that Washington was still pursuing a two-part strategy which included the threat of military strikes. "We don't want to take the bullet out of the gun because we don't trust this guy," the official said.
Mr Solana said "progress has been made", after Mr Holbrooke briefed the allies in Brussels. But he added: "After a thorough review of the situation in Kosovo, we see that the Yugoslav government still has not complied fully with UN Security Council resolution 1199 in a way that can be verified.
"I still believe diplomacy can succeed and the use of military force can be avoided," Mr Solana told an early morning press conference.
"But the responsibility lies on the shoulders of Milosevic. He knows what he has to do."
The vote on the critical "activation order" giving over military control to the Supreme Allied Commander for Europe had been anticipated yesterday, even as reports trickled in of progress in the Belgrade talks that could avert war in the Balkans.
Mr Holbrooke, who made a lightning trip here from Belgrade late Monday night to brief the NATO ambassadors, said he was returning to the Yugoslav capital for more talks with Milosevic later today.
Speaking after briefing NATO allies on his talks, he said he would meet the acting OSCE president, Mr Bronislaw Geremek, the Polish Foreign Minister before returning to Belgrade.
On his arrival in Brussels Mr Holbrooke said, "We are not talking about a deal . . . we are discussing the situation in Kosovo in intense detail."
Despite the arrival in Britain of US B-52 cruise missile-carrying bombers at the weekend, and the amassing of more than 400 aircraft to strike Serb targets, it was becoming clear that a key sticking point was the presence, composition and mandate of ground forces to protect ethnic Albanians.
Even the most hawkish NATO members have emphasised that the objective is humanitarian, warning of the limited effect of military action.
Journalists in Kosovo yesterday reported the withdrawal of 500 Serb police officers from the Klina sector in the central Drenica region of Kosovo.
NATO is demanding the implementation of a September UN Security Council resolution which calls for the withdrawal of Serb security forces, an immediate ceasefire, the return of refugees to the homes and access for humanitarian organisations.