The issue is back on the agenda.

At what stage should Nato be prepared to send ground troops into Kosovo to "finish the job"?

Whenever this issue arises, it is vital to ask the question - are we talking about ground troops to fight a war?

If we are, then the answer is that Nato does not intend to fight a ground war.

The United States would have to take the lead and right at the start of the air war, President Clinton said he was not going to send American troops into battle on the ground.

That remains his position.

A third way

But there is a grey area between not going in to fight and not going in at all, and this is where the debate is going on.

Destroyed oil storage facility in Nis: Nato claims considerable success in its air mission

This "third option" is now being examined in much more detail.

Could a situation arise in which the Yugoslav army in Kosovo had virtually collapsed or has even begun a withdrawal?

Could Nato not seize that opportunity and make a rapid entry even in the absence of a full peace agreement?

The British Foreign Secretary Robin Cook, who has emerged as one of the hawks in this conflict, seems to suggest so.

BBC Diplomatic Correspondent Rageh Omaar reports on growing calls for a ground force

He said on Monday that the Nato Secretary General Javier Solana was "reviewing when we could take advantage of the success we are having.."

This would suggest that Britain, for one, would be keen to build up Nato forces in Macedonia and Albania now, in order to prepare for a possible move into Kosovo this summer.

This would give time for the refugees to get back and rebuild some shelter at least before the winter.

Peace force for Kosovo

Mr Cook will be meeting the US Secretary of State Madeleine Albright in Washington this week.

The BBC's Paul Reynolds: "There is also the question of the timetable for moving troops"

There is no clear agreement yet on how this third option might be exercised.

Some in the alliance are wary that a build up of troops to keep the peace in Kosovo (a concept which has always been part of Nato thinking) could, by mission creep, turn into an invasion force. And that, they don't want.

But planning for a new KFOR - Kosovo peacekeeping force - is underway.

The Pentagon spokesman Ken Bacon said that work in Nato started last week.

This new force would probably be bigger than the 28,000 strong force originally foreseen (and elements of which are already in Macedonia).

He also indicated that peace would have to come before the force could be moved in.

The Powell doctrine

In the meantime, Nato relies on air power alone.

This has drawn criticism from the man who won the Gulf War, retired US General Colin Powell.

The "Powell doctrine" laid down that overwhelming force should be used in pursuit of a clearly defined political objective. This, he says, has not happened in Yugoslavia.