Britain is willing "in principle" to lead an international stabilisation force in Afghanistan, the Prime Minister confirmed today.
Up to 1,500 troops could be sent, although figures had not yet been finalised, Tony Blair told the Commons.
UN authorisation for the force is expected later this week, he said in a statement on the weekend's EU council meeting.
"We would hope to have lead elements (for the force) in place shortly."
Mr Blair said the fight against terrorism had been uppermost in the minds of those attending the summit. There had been unanimous support for the military action in Afghanistan "and a determination to continue our efforts to root out the al Qaida network".
He said that the video of Osama bin Laden, released last week, "demonstrates his guilt beyond any reasonable doubt whatsoever.
"It brought home the sheer evil of bin Laden and his followers and their sick pleasure in the murders which they have committed.
"I don't believe that anyone can now dispute that ridding the world of the al Qaida terrorist network is a job in the interests of us all."
Later the Prime Minister said there may be some "lead elements" of a peace keeping force in Afghanistan by the time the interim government was in place - next Saturday, December 22.
Earlier Mr Blair said there had been strong support for the deployment of an international assistance force to maintain peace and stability in the region.
The details of such a force must await the outcome of meetings in Kabul between an international military team and the interim authorities.
"But ... Britain is willing in principle to lead such a force.
"It is likely to comprise troops from various countries, European and others.
"Friday's meeting of potential troop contributing nations was attended by a number of EU countries as well as Argentina, Australia, New Zealand, Canada, the Czech Republic, Jordan, Malaysia, Turkey and the US.
"The British contingent is likely to be up to 1,000 to 1,500, though I stress that this is not yet decided.
"The US has given its full help and support for this security force."
Mr Blair said: "There has been a brilliant victory over the Taliban. That is a welcome liberation.
"But we know that is only the start of enabling Afghanistan to cease being a failed state and become a responsible partner in the region.
"The situation in Afghanistan remains fragile. The new political process remains in its infancy.
"There is an urgent need to ensure that as the war is being won we play our part in securing the peace."
Mr Blair also denounced the "continuing and appalling violence" in the Middle East.
"In our view, and that of all our partners, the only basis for peace in the Middle East is full recognition of Israel's right to live in peace and security and the establishment of a viable Palestinian state."
Tory leader Iain Duncan Smith warned British troops could become a target for Taliban stragglers if deployed as peackeepers.
The Conservatives held "deep misgivings" about Britain leading a peacekeeping mission in the war-torn country
"In reality we already have troops on the ground with the US carrying out search and destroy against elements remaining of the Taliban as well as al Qaida.
"What concerns me is there are still elements of Pastun who are unhappy about the settlement and there are of course going to be members of the Taliban who will find an opportunity to pick a target themselves in that peacekeeping process that may allow them to get their own back."
Mr Blair responded saying the international community could not turn its back on Afghanistan a second time.
"If the international community walks away from Afghanistan now it will make exactly the same mistake that was made 10 or 12 years ago when it left Afghanistan to become what it became - a failed state."
He said a time limit on action had not been agreed but added: "At the moment people are talking in terms of several months, so that would be the British forces there not on a long term basis, just to get the security force going."
He confirmed there could be "some lead elements" in place by December 22, when the interim government started operating.
"The fact is we are the nation best placed to give that leadership, which is why we have been asked to do it."Reuse content