NATO's theatre of operations was widened yesterday from the tiny province of Kosovo when the Czech and Slovak governments approved military movements across their territory - a development which could open the way for an eventual invasion of Serbia from the north.
Bulgaria's government defied demonstrators and opinion polls to approve NATO's use of its airspace, in return for NATO security guarantees, as over 40 heads of government from NATO allies and partners began heading for tomorrow's three-day Washington summit at which crucial political decisions on the next phase of the war will be made.
The tangible support of the Czechs as new NATO members, and of Slovakia and Bulgaria as candidate members of the alliance, came as the pace of the air war intensified.
Apache tank-hunter helicopters started to deploy in Albania, and NATO announced that its warplane reinforcements now meant that twice as many all-weather strike missions were being flown as in the first weeks of the campaign.
NATO has also expanded its target list in Yugoslavia, warning yesterday that "any aspect of the power structure is deemed a legitimate target".
"We will go after the targets that make him [Mr Milosevic] what he is." said the NATO spokesman, Mr Jamie Shea. Hitting his party HQ was "a powerful reminder that there is no sanctuary for any of his power structure".
A British government spokesman yesterday confirmed that the British Prime Minister, Mr Blair would be discussing the deployment of NATO ground troops into Kosovo "sooner rather than later" when he sees President Clinton at the White House.
Mr Blair told the British House of Commons that sending ground troops in against an "un-degraded" Serbian military machine posed "formidable" difficulties. But he insisted: "Milosevic does not have a veto on NATO action. All options are always kept under review - that is sensible for us to do." He also told MPs that Russia had a significant part to play in trying to bring the conflict to an end.
US administration officials said yesterday they expected a request from the NATO supreme commander, Gen Wesley Clark, to update a study prepared last year on the possible use of ground troops.
The UK's Defence Secretary, Mr George Robinson, was asked earlier at a UK Ministry of Defence briefing whether he expected that a declaration at the NATO summit would include a reference to the use of ground troops.
He replied: "The position on a forced invasion, a wholesale, opposed invasion remains as it was at the beginning, but I use my words this morning with some care."
Mr Milosevic said in an hour-long CBS TV interview last night - the first since the air campaign began - that the three American airmen captured by Serb forces were in good health and were being treated well.
Earlier in the day, the Czech army chief of staff, Gen Jiri Sedivy, said the first NATO transport could cross Czech territory as early as today.