Six Jaguar ground attack aircraft left RAF Coltishall in Norfolk for Italy to take part in the live-fire exercises, codenamed Determined Falcon, over Albania and Macedonia. Mr Robertson said: "This is diplomacy backed by the threat of force which worked against Saddam Hussein and hopefully will work against Slobodan Milosevic."
The threats against the Yugoslav president were backed by France and Germany. After a meeting with the main Kosovo Albanian leader, Ibrahim Rugova, the French President, Jacques Chirac, said: "I hope that we can obtain the cessation of hostilities and the Serbs' aggression in Kosovo. Otherwise, all means, including military means, will have to be used,"
The German defence minister, Volker Ruhe, said Germany would be sending six aircraft to participate in the Nato exercise. "If Milosevic does not immediately call off his criminal ethnic cleansing through expulsion and murder, it may not stop at air manoeuvres," Mr Ruhe recently told Bild am Sonntag.
Denmark said it would send two fighters to take part in the exercises over Albania and Macedonia, which immediately adjoin Kosovo.
Nato sources suggested that the exercises would probably start today, though the US Defence Secretary, William Cohen, insisted that no time had yet been set, though it would probably be "in the next few days".
The Russian President, Boris Yeltsin, is scheduled to meet Mr Milosevic on Tuesday to convey the strength of international concern. Russia has repeatedly insisted, however, that it is against military action.
The United States has suggested that a United Nations resolution on the use of violence, which could be blocked by a Russian veto, is not necessary. Mr Cohen argues that "to subordinate Nato to the UN is inadvisable and not necessary."
Western leaders now say that they are determined not to leave things in Kosovo too late, as happened in Bosnia, where the threat of military force came only after the worst slaughter was already over.
Many observers, however, believe that it might already be too late to prevent a conflagration in Kosovo, where the Albanian commitment to violence has risen sharply response to killings by the Serbian police force in recent months.
Robert Fisk, pages 20, 21Reuse content