War In The Balkans: US troops freed but Nato is unmoved Serbia

DESPITE THE release of the three US soldiers and fresh stirrings on the diplomatic front, Nato vowed last night to keep up the bombing war until Slobodan Milosevic starts to pull his troops out of Kosovo and agrees to a strong international force in the province.

Hours after the civil rights leader Jesse Jackson triumphantly led the three across the border into Croatia, from where they were flown to Germany, President Bill Clinton declared the US's "resolve to persevere" until more than a million Kosovo Albanian refugees could also return home.

The point was underlined within hours last night when much of Serbia, Reuters reported, was plunged into darkness after Nato warplanes hit facilities at a key power plant west of Belgrade.

Residents said the power was out from Nis in the South to Sombor near the Hungarian border in the north, affecting millions of people. It was the most disruptive blackout so far in the six-week-old bombing campaign.

"People can endure for a while," said one Belgrade woman. "But if you think about it, the refrigerators and deep freezers are full of food - this gives you a real sense of war."

In London, George Robertson, the Defence Secretary, expressed regret for the accidental bombing of a civilian bus as it crossed a bridge in Kosovo, which the Serb media said caused up to 60 deaths. It was the darkest blot for Nato on a weekend which also saw the loss of two of its planes - the first since an F-117 stealth bomber crashed on 27 March, three days after the war began.

In the most spectacular incident, a US F-16 jet suffered engine failure, according to a Nato spokesman, and crashed in western Serbia at 1am BST yesterday. Two hours later the pilot, who had ejected, was rescued by special Nato forces.

The other loss was of a US Harrier, which plunged into the Adriatic near Brindisi during a training exercise on Saturday. Again the pilot was picked up alive from the sea - meaning the alliance has yet to suffer a casualty.

Tony Blair tonight starts a two-day visit to Romania and Macedonia, aimed at shoring up support for Nato and assessing the plight of the hundreds of thousands of refugees just across Kosovo's borders.

As Nato proclaimed its determination to keep the pressure on Mr Milosevic, the pace of diplomatic activity was again picking up, amid more conflicting signals about President Milosevic's readiness to accept a strongly armed force in Kosovo as part of a peace settlement.

In Belgrade a foreign ministry spokesman again insisted that any peace- keepers should be lightly armed and only some 2,000 to 3,000 strong, even as talks in Vienna between a US congressional delegation, Russian officials and an aide of the Yugoslav president purported to have reached an outline agreement for armed foreign peace-keepers to move in.