And the UK has pledged an additional aircraft carrier, HMS Invincible, and two support ships to the region.

The Ministry of Defence said sending Invincible was part of 'tightening the screw' on the Serbs

The announcements came as air raid sirens sounded in the Serbian capital Belgrade, hours before the country marks one of its main religious festivals, Orthodox Easter Sunday.

Defence corespondent Mark Laity: "Nato preparing for a long war"

In Saturday's daily briefing, the Pentagon spokesman Kenneth Bacon said the US will be sending 82 more warplanes to join nearly 400 US attack and support planes already in the region.

Among the additional hardware, the US is committing:

• 24 F-16 fighters armed with Harm radar missiles
• four A-10 attack aircraft
• six radar-infiltrating EA-6B aircraft
• 39 KC-135s
• two KC-10 refueling tanker aircraft
• seven C130 transport planes

But there was no word from Washington on whether ground troops will be sent in.

Bad weather delays Apaches

In the briefing, US officials acknowledged that it could be several weeks before 24 Apache attack helicopters can be deployed against the Serbian forces.

News 24 rounds up the latest news from the region

Bad weather has forced delays in the movement of support equipment for the Apache helicopters to the Albanian capital, Tirana.

Introduction of the Apaches will allow close-to-the-ground strikes against Serb troops and tanks during persistent bad weather.

Nato said that it had to cancel a third of its attacks as a result of heavy cloud cover on Friday night.

Apache helicopters will allow close ground support

But the official Yugoslav Tanjug news agency said missiles struck a railway station in the town of Kosovo Polje early on Saturday, and the airport at Slatina, southwest of Pristina was hit, later in the day.

Explosions were also reported in Belgrade and around the towns of Novi Sad, Nis, Cacak and Bor.

Meanwhile, Serb forces and KLA guerilla fighters have exchanged fire near the Albanian border, according to an OSCE spokesman.

Four KLA fighters were reported killed and two wounded in a battle on Friday, around 300km north of Tirana.

Diplomacy continues

Western leaders have stepped up efforts to involve Russia in a diplomatic solution to the Kosovo crisis.

The Italian Prime Minister, Massimo D'Alema, has spoken to President Yeltsin about using Russian influence to persuade Yugoslavia to accept a United Nations plan to end the Kosovo crisis.

The German foreign minister, Joschka Fischer, said he was trying to arrange an emergency ministerial meeting of the eight leading industrial nations, the G8, to involve Russia as a mediator in the crisis.

The move comes one day after President Yeltsin raised the possibility of Russian military involvement in the conflict in Yugoslavia.

The UK and the US have reportedly since received assurances from Moscow that Russia had no such intention.

Ethnic cleansing fears

Duncan Kennedy reports from Albania

The expulsion of refugees from Kosovo has started again, prompting fears of a new wave of ethnic cleansing.

International monitors say between 3,000 and 5,000 people are being forced across the border in the second wave of forced expulsions since Friday.

Kosovo Albanian refugee children play with toy guns

More than 1,500 people from a village near the capital of the province, Pristina, crossed into Albania on Friday night.

And hundreds of refugees have been arriving in Macedonia, although at one crossing point, the Yugoslav authorities turned back a line of vehicles that eyewitnesses said stretched for miles.

Although the United Natiuons High Comissioner for Refugees has urged that refugees be kept in the region if possible, more than 700 were flown from Macedonia to Germany and Poland on Saturday.

Other top stories

• New exodus from Kosovo
• Montenegro rejects censorship
• Orthodox Easter under the bombs
• Propaganda war hots up
• Picture gallery: Life in the camps

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