British troops are to be sent to Afghanistan to join an international peacekeeping force.

The government will officially announce on Tuesday that up to 3000 troops will join the UN presence during a visit by US secretary of state Colin Powell.

Subject to the agreement of the provisional Afghan government, Whitehall officials say "a limited number of troops" would be deployed on the ground, equipped with Warrior armoured vehicles.

They stress that such a mission would be hugely dangerous.

The UN force is also likely to be made up of forces from Germany, France, Canada, Australia, as well as Muslim nations such as Turkey, Bangladesh, Malaysia and Indonesia.

Parliament will be asked to endorse the deployment of British troops in a UN peacekeeping force, as the UK signals its willingness to play a leading role in the reconstruction of Afghanistan.

Geoff Hoon yesterday said that a request from the UN will be taken "very seriously" by the UK.

"I see every advantage in one country providing the main elements of the headquarters of this operation, something that the UK has done very well in the past," he said. "We certainly want to help. We have won the war; it is important that we win the peace."

US vice president Dick Cheney has indicated that the US will play a more limited role in the international force. "We might provide some light support for it", he said.