Allied commanders in Brussels promised to "tighten the noose" around Slobodan Milosevic's war machine and in London the Ministry of Defence released graphic footage of RAF Harriers blowing up a munitions dump in Pristina.
The attack, on facilities of the Serbian military police, was aimed specifically at those carrying out repression and ethnic cleansing in Kosovo. But the most pressing question, according to military analysts, is just how long Nato can defer using ground forces poised on the Yugoslav borders.
Publicly, both the British and American governments continued with the party line that they had no intention of introducing the troops, who would include British soldiers based in Macedonia.
In London, the Foreign Secretary, Robin Cook, denied that the extensive publicity being given to atrocities by Serbian forces in Kosovo was preparing the public for the inevitable introduction of the ground forces.
The White House said it was not in favour of sending in troops, despite what it called a "textbook case of ethnic cleansing" by Serb government forces and paramilitaries. A spokesman, Joe Lockhart, said: "We feel that we can meet our military objectives through the Nato air campaign."
For now this includes intense attacks on Serb armour and heavy artillery inside Kosovo, with increasing use of the A-10 "Warthog" tankbuster ground attack planes. Several were seen taking off yesterday morning from Aviano air base, in Italy, along with a number of F-16s. The A-10s can operate by day or night and are known to be extremely effective against armour. But they are low and slow-flying and thus would be vulnerable to Serb anti-aircraft fire and missiles.
The RAF Harrier GR7s, which were shown on film destroying three buildings in Pristina, are part of phase two of the military operation - the use of tactical ground attack planes. The Chief of Defence Staff, General Charles Guthrie, said: "The tempo of operations is getting faster and the focus of our operations is shifting towards actions against the forces implementing Milosevic's policy of repression in Kosovo and the infrastructure behind it."
Introducing photographs taken on board the Harrier GR7s, Group Captain Steve Parkinson explained how each of the three pilots had operated "autonomously" to take out buildings at the site. The first two bombs were on target but on the third attempt, one of the two bombs used "did not impact properly", landing on an area of open ground. The base was being used for the "processing and storing" of ammunition for several types of weapons.
President Bill Clinton returned to the White House from Camp David yesterday for emergency consultations with his national security staff, as growing evidence emerged that the conflict in Kosovo was spinning out of Nato's control.
Some congressmen suggested that action other than air strikes may be needed, but there was little indication that this opinion was widespread. Senator John McCain, a Republican, said that the US had to "exercise every option", adding that if the threat of ground forces was raised against Mr Milosevic, "it could lend impetus to convincing him that he cannot win".
Other senators insisted that if there were to be ground forces, they should be European, not American. If legal experts from the State Department say that genocide is occurring, they may shift ground. Under a 1948 UN treaty, every signatory state has a duty to prevent such a crime, and many legal experts say that this includes military intervention.
The Yugoslav army claimed it had lost just seven soldiers in five days of Nato strikes while shooting down seven alliance planes, three helicopters and about 30 missiles.
The claims have been denied by Nato.
Lieutenant-General Spasoje Smiljanic, commander of the Yugoslav air force and air defence system, said Nato had under-estimated the readiness of the Serbs to defend their country, regardless of the number of casualties. He claimed that Nato, after hitting exclusively military targets until Saturday, had started dropping bombs and missiles on infrastructure and civilian targets, including schools, hospitals and refugee centres. "My country will defend itself to the last man and to the last combat means at our disposal."
Yesterday, Macedonia's Foreign Minister appealed to the European Union and Nato for rapid economic and military assistance. Aleksander Dimitrov said Yugoslav forces had closed in on the Macedonia border and neither his country nor the 12,000 Nato troops there had sufficient military capability to defend Macedonia.Reuse content