British Prime Minister Tony Blair said Tuesday that a U.N. presence is required in Afghanistan "as soon as possible" to begin building a broad-based, stable coalition to replace the fleeing Taliban regime.

Blair said he believes the Northern Alliance forces that have taken Kabul will accept sharing power in a new government, because that was a condition of the U.S. bombing that paved the way for advances on the ground.

"I think that you will find, as the situation progresses over the next few days, that everybody understands that the successor regime in Afghanistan has to be broad-based to be successful, because there are large numbers of Pashtun people who, particularly in the south of the country, who have to be involved in any successor regime," Blair said.

"And it is necessary also to make sure that any successor regime is a stable partner for the surrounding countries in the region," he added.

Blair said he had spoken Tuesday to U.N. Secretary-General Kofi Annan about the necessity of accelerating work on a successor government.

"That process is well advanced. It is only now with the military direction so clear that I think we are in the right position to be able to bring together the various ethnic and other factions likely to be involved in the formation of any successor government," Blair said.

"I believe we can, therefore, that we can make real progress toward the filling of the current power vacuum in Kabul. But we need a U.N. presence there as soon as possible," Blair said.

He said the U.S.-led coalition had not yet achieved its objectives, which included smashing the Al Qaeda network of Usama bin Laden.

"Whilst the military strategy is vindicated, and whilst we join in the celebrations of the people of Kabul and the other towns and villages from which the Taliban have fled, our forces know, and I know, that this is only setting the conditions in place for our objectives to be achieved," Blair said.

"Usama bin Laden remains at large, so do his closest associates. The Taliban regime are not yet fully dislodged from oppressing the people of Afghanistan and shielding Al Qaeda.

"However, that task will now be eased by the scale of defections taking place, the ground being gained and the intelligence being gathered," Blair said.

Blair said British officials believe bin Laden is still in Afghanistan.

"And as for our ability to catch up with him, that has obviously increased as the power and authority of the Taliban regime that was shielding him was destroyed," he said.