By Barnaby Mason BBC diplomatic correspondent

Intensive international discussions are continuing about what should happen in Afghanistan after the fall of the Taleban - even though the outcome of military operations is still very unclear.

In a speech in London, the UK Foreign Secretary, Jack Straw, has said the United Nations should play the leading role in any transition, and a multi-national force might be required to provide security.

Mr Straw said there was now agreement among Afghanistan's neighbours that a broad-based government was the right solution, that the domination of Mullah Mohammad Omar and his faction cannot simply be replaced by another.

It is true that the phrase "broad-based" is on everyone's lips. But there is no agreement on what it means.

No conclusions

The Iranians say the Taleban can have no place in a new coalition, a position also taken by India and Russia.

Russian President Vladimir Putin said the Afghan regime had been compromised its co-operation with international terrorism.

Mr Putin has voiced strong support for the Northern Alliance

After talks in Tajikistan, he repeated his support for the opposition Northern Alliance, describing it as the internationally-recognised government.

The United States has not given the Northern Alliance whole-hearted support, and has appeared to go along with Pakistan's suggestion that more moderate members of the Taleban could have a role to play.

Mr Straw avoided the issue; he said the form of a future government and the process of establishing it was up to the Afghan people.

That included, he said, the question of whether the exiled King, Mohammad Zahir Shah, could act as a figurehead.

Ready for speed

Mr Straw said Britain was working with the UN, international partners and Afghan representatives to formulate a robust plan.

They might need to move quickly, he warned, as the end of the Taleban regime might come gradually, area by area, or very suddenly.

Mr Straw acknowledged the dangers by saying that troops might be needed to provide security - either a UN force or some other multi-national body.

He did not rule out non-Taleban Afghan forces playing a role.

The message from all of this is that a lot of thinking is going on but no firm conclusions have been reached.

The diplomacy risks being left behind by events on the ground and the rival Afghan factions are unlikely to fit neatly into the plans being made.