Tony Blair has said Britain stands "willing" to lead a UN peace-keeping mission in Afghanistan.

The move came as the US secretary of state, Colin Powell, held talks with Blair in Number 10.

"Once the military campaign has achieved its main objectives - and we are certainly in the course of doing that now - then it is important that we maintain the humanitarian and political track. We have indicated in principle that we are willing to play a leading role in any UN-mandated force to provide stability in Afghanistan," Blair said.

The US secretary of state is said to have used a short visit to Number 10 to press Blair to take the lead in a ground-based mission to stabilise the country.

Speaking in Paris ahead of his visit, he stressed that Britain should take a lead role in keeping the peace in a post-Taliban Afghanistan.

"I'm pleased the United Kingdom is willing to step forward and volunteer for a leadership role," Powell told a news conference.

However, Blair refused to say exactly when he would announce Britain's next move.

"There are still an immense amount of details to be decided and discussions to be had and we are really not in a position to go into the details of any such mission at this stage," he said.

Speaking earlier in the day a Number 10 spokesman said Britain could not be seen to be acting alone.

"We are very pleased that Colin Powell has such a high opinion of our contribution that he wants us to do more. We welcome that. But equally it would be totally wrong for us to be unilateralist about this in any way. We have to coordinate our efforts with the UN, coordinate our efforts with Afghanistan, and with our other allies, and that we continue to do," the spokesman said.

Downing Street has also denied that it is at odds with the US administration over the next phase of the war on terror.

"It would be easy to turn this into some kind of Punch and Judy show but the reality is that it ain't like that - the reality is multi-faceted," said a spokesman.

Following a short round of talks, Blair and Powell appeared in Downing Street for an act of remembrance.

Three months to the minute since the first attack on the twin towers, the two leaders listened to American schoolchildren playing the British and US national anthems.