The Telegraph reports:

Western forces, which could include British troops, must be sent into the Balkans to prevent Russia sparking a new European war, according to David Cameron [pictured]. Speaking in Washington, the Conservative leader will issue a stark warning that Russia's increasingly assertive foreign policy is jeopardising Britain's national security. Mr Cameron fears a diplomatic and military crisis could arise over Kosovo, the province of Serbia which has effectively been a United Nations protectorate since Nato invaded to stop ethnic cleansing by Serb forces in 1999. The ethnic Albanian government of Kosovo is threatening to declare independence from Serbia on Dec 10. Moscow is backing Serbian attempts to block the declaration, while the United States and the European Union are in favour.

"Let me make it clear: there could be a new crisis in the Balkans by Christmas," Mr Cameron will say in a speech to the Brookings Institution, a Washington think-tank. "That is a direct threat to our national security, and we must therefore take decisive action now to prevent it. We need to reinforce the military presence in the region now, by drawing on some of Nato's dedicated operational reserve, to prevent trouble later."

Nato members take it in turns to provide a reserve force to back up the alliance's K-For peacekeeping force in Kosovo. The reserve is currently led by a battalion of Italian troops with a German battalion next in line to deploy. But from Jan 1, Britain takes on responsibility for providing the "lead-ready" battalion for the reserve, putting British troops first in line to deploy.

Tory officials made clear last night that Mr Cameron was not calling for the deployment of extra British troops above and beyond those already committed to the Nato Reserve force. But they also said that the Tory leader had not made his call lightly, saying it was a measure of how seriously he takes the need to prevent more instability in the region. British diplomats privately share Mr Cameron's fears of a Balkan crisis, but ministers have stopped short of proposing a further military deployment, and the Tory leader's call could dramatically increase the diplomatic stakes over Kosovo. But he will insist that intervention is vital to British national interest because instability in the Balkans could bring a wave of immigrants to Bitain, and make the region a breeding ground for al-Qaeda. He will say: "Instability in the Balkans, with all the dangers that would bring, would be a threat to us all."

The last British troops in the Balkans, a 600-strong force of Welsh Guards, left Bosnia in March. Since 2003, a handful of British military officers and police personnel have been in Kosovo training and advising local security forces. Mr Cameron will make his speech as part of a visit to meet President George W Bush in an encounter designed to rehabilitate the Conservatives after years of isolation in Washington. Mr Cameron's 45-minute private meeting with Mr Bush at the White House will heap more misery on Gordon Brown as he faces the mounting scandal over party funding and increasingly poor opinion polls.