Nato governments have said they will make sure the flood of refugees currently pouring out of Kosovo will be allowed to return.

Various plans have been mooted: a Nato invasion of Kosovo; a protectorate guaranteed by the international community; safe havens; or defended corridors.

But are any of them viable?

On the second point, there is a recent example of an international protectorate in the Balkans - the UN transitional agreement for Eastern Slavonia.

Eastern Slavonia is a strip of Croatian land which was overrun by the Serbs. It had seen some of the grimmest fighting of the war in Croatia.

But in late 1995, Croatia had turned the military tide, the local Serbs had been largely cut adrift by President Slobodan Milosevic in Belgrade and the two sides agreed to a UN transitional administration in Eastern Slavonia.

'Co-operation is vital'

The man who would become the UN Transitional Administrator, virtually the viceroy of Eastern Slavonia, Jacques Klein, was clear at the time about why such a deal was possible.

What future for Kosovo's children?

"The key is the co-operation of the two principals. In other words if Croatia and Serbia agree that this should be done and we have the co-operation of the two sides then it can be done," he said.

To back him up, Jacques Klein had, amongst other things, 5,000 heavily-armed troops.

Mats Berdal, a specialist on Balkans peacekeeping at St Antony's College, Oxford, says the eastern Slavonia experience was an important departure from previous UN operations in the region.

"It was a much more powerful force. One which had considerable ... military resources at its disposal and in which the person in charge of the transitional authority was able to do pretty much as he wanted during that particular transtiional period."

Nato stands firm

On Kosovo, Nato insists its objectives for now remain what they have always been:

• a democratic, peaceful, multi-ethnic Kosovo

• Yugoslavia to stop the repression and expulsion of the Kosovar Albanians

• the provision of an environment in which all refugees are able to return without fear of further intimindation or repression

Publicly at least, Nato says there is still no question of it fighting its way in to Kosovo. So does an agreement along the lines of eastern Slavonia present a possible solution?

According to Mats Berdal, there is one important problem.

Hundreds of thousands left their homes

"Eastern Slavonia was always going to go back to Croatia. So the issue of contested territory was never an issue during the transitional period," he said.

"The Croatians had effectively won the war, Milosevic had agreed in advance that this territory was going to go back. So what the UN transitional authority was charged with doing was really to oversee the peaceful transition of that territory."

The Eastern Slavonia experience has meant some, if not all displaced Croats have returned. But it has not persuaded many Serbs to stay.

Mats Berdal says the UN operation has certainly allowed for a peaceful handover of the territory, which might not have been the case, but it has not stopped what one western official has called "soft ethnic cleansing".

However the Kosovo Albanian refugees are persuaded to return, it seems clear it will require a significant, possibly open-ended western commitment.