NATO air strikes against Serb military targets are imminent following the order to the alliance commander to launch the first wave of attacks. And President Clinton has warned that American lives will now be at serious risk.
The NATO Secretary General, Mr Xavier Solana, announced in Brussels last night that he has ordered the Supreme Commander, Gen Wesley Clarke, to "initiate" military action against Yugoslavia. The first strike will be cruise missiles, probably from US aircraft based in Britain and from ships in the Mediterranean.
Earlier yesterday Mr Clinton admitted that the last-ditch talks between his special envoy, Mr Richard Holbrooke, and President Slobodan Milosevic of Yugoslavia had "got nowhere" as the envoy left Belgrade to fly to Brussels to brief NATO ambassadors.
Mr Holbrooke said in Brussels that diplomatic action had failed and the process was now "handed back to NATO".
In Belgrade, several foreign embassies were evacuating their nationals late last night and European airlines cancelled flights into the city from today.
Yugoslavia announced the call-up of thousands of reservists and the president of Serbia, Mr Milan Milutinovic, struck a defiant note saying that NATO troops would never be accepted in Kosovo.
As Mr Holbrooke left Belgrade for Brussels he said that Mr Milosevic could telephone him if he wanted to prevent NATO bombings.
It was a call that Mr Milosevic showed no signs of making late last night as US, British, French and Italian forces readied themselves for attack.
In Kosovo itself, columns of smoke rose from the homes of ethnic Albanian families set alight by Serbian forces which clashed with separatist rebels on two fronts.
As reports emerged of arbitrary killings of civilians, freshly-lit fires burned fiercely through the roofs of abandoned homes in Gornja Klina, some 50 km north-west of the regional capital Pristina.
Heavily-armed Serbian military police could be seen walking through the debris and a burnt-out car smouldered by the roadside. More smoke rose on the horizon from Srbica, a town seized by Serb forces on Saturday and closed since to independent observers.
President Clinton in a speech aimed at mobilising US opinion behind military action, said that "if you don't stand up to brutality and the killing of innocent civilians you invite them to do more."
Warning that NATO was ready for action, the President said: "If President Milosevic is not willing to make peace, we are willing to limit his ability to make war on Kosovo."
Mr Clinton's speech was also aimed at heading off a vote in the Senate threatening to cut off funding for US involvement against Kosovo as part of the NATO operation. Following a briefing with the President, senators indicated that they would now vote in support of US intervention but doubts were expressed about the success of air strikes alone.
As the crisis deepened, the Russian Prime Minister, Mr Yevgeny Primakov, suddenly cancelled his planned visit to Washington as he was in mid-Atlantic and returned to Moscow after he had spoken to Vice-President Al Gore.
A report that Russian Mig aircraft were detained in Azerbaijan while on their way to Yugoslavia in defiance of an arms embargo was denied by the Foreign Ministry in Moscow.
The FAI will formally seek a postponement today of the Republic of Ireland's European Championship qualifying game in Macedonia despite UEFA's insistence that the match should go ahead as scheduled.