In Brussels, defence ministers of the 16-nation alliance instructed their military commanders to draw up plans to "halt or disrupt" the fighting in Kosovo, which has taken at least 300 lives this year and forced more 50,000 people to flee their homes.
But in Kosovo itself, there were reports last night that Serbian forces may be about to start another offensive. Unconfirmed reports said troops and security police were planning to attack guerrillas of the Kosovo Liberation Army, east of the town of Klina, in an area that has been under effective KLA control for over a month.
Meanwhile in a diplomatic move which could hold the key to a peaceful solution, President Boris Yeltsin of Russia, Serbia's Orthodox ally, will meet Mr Milosevic in Moscow to press him to reach a political settlement.
Insisting the West would not tolerate another Bosnia, George Robertson, Britain's Secretary of State for Defence, said that Mr Milosevic would be "rash and foolish" to dismiss the warnings. "All options are available to us," he declared, "We are ruling nothing in and nothing out."
Among those options is direct intervention on the ground, though this is plainly a last resort. Air strikes were the "natural" choice, Mr Robertson said, but other possibilities include electronic warfare, a no-fly zone , and a no-entry zone for heavy military equipment.
In London today, the six- nation Contact Group - Britain, the US, Russia, France, Germany and Italy - will demand an immediate end to the violence, the withdrawal of special Serbian police units, the resumption of genuine political negotiations on a new status for Kosovo, with international mediation if required, and full access to humanitarian groups and war crimes investigators.
Thus far, such demands, and an array of economic sanctions, have been ignored by Mr Milosevic, and last night the response to Nato's latest moves was as truculent as ever. "We are a sovereign country," said Ivica Dacic of the ruling Socialist party, "Without our consent, no actions of any international alliance can be carried out on our territory."
But never has the threat of military force been as clear cut. Live-fire Nato air exercises over neighbouring Albania and Macedonia could start within days, and the German Defence Minister, Volker Ruehe, spelt out that if air strikes went ahead they would be aimed not only at Serb targets in Kosovo, but across Yugoslavia.
The Yugoslav air force still has about 30 serviceable MiG29 aircraft in two separate squadrons, but has only obsolete radar cover and ground- to-air systems, which could be disrupted by Nato jamming.
The unknown remains Russia, opponent of both military intervention and economic sanctions, and the one mediator that Mr Milosevic - though not necessarily the West - might trust. British officials hope today's talks will produce a common stand that Mr Yeltsin will present to Mr Milosevic.
If not, then things become more complicated. Prior approval by the United Nations for Nato military strikes ("desirable" but not absolutely necessary, William Cohen, the US Defense Secretary, claimed yesterday) could be blocked by a Russian veto, casting doubt on the legality of the enterprise.
"My father worked here as a council official ... until the Serbs fired all the Albanians nine years ago," a young girl whispered beside me. "Now he stays at home and rests."
Robert Fisk reports from Kosovo, page 13Reuse content