It is far too early to know if the Belgrade Government's proposed ceasefire is a genuine prelude to a peace deal or a tactical ploy intended to stall the Nato air campaign just when the weather is improving.

Either way, the initial response of key Nato governments has been negative.

Both London and Washington insist it falls far short of Nato's demands - the Alliance insists that there are several conditions for a halt to its air attacks.

Nato's conditions

These were stated most bluntly by the Pentagon spokesman Kenneth Bacon yesterday evening. He said that Mr Milosevic had to stop the fighting; and withdraw his forces from Kosovo "so they don't remain there holding this empty territory" as Mr Bacon put it.

He said that Belgrade had to accept a Nato-led peacekeeping force; accept democratic self-government for Kosovo and allow the refugees to return.

Their return is seen by Nato as absolutely linked to the presence of an international peace-keeping force.

No Rambouillet reprise

While not openly acknowledging it, Nato's basic position has moved on from the failed Rambouillet peace plan.

That envisaged a drastic reduction in the numbers of Yugoslav troops and police in Kosovo; those remaining being returned to barracks.

Many of those barracks have now been bombed by Nato warplanes and the Alliance's message seems to be that it will only pause in its offensive when it sees Yugoslav units preparing for a full-scale withdrawal.

Why now?

It is difficult to speculate on the motivation behind this offer. It could perhaps be the first sign that Nato's air campaign is beginning to hit home.

The attacks on Serbia's infrastructure - its petrol depots, key bridges and so on - is clear evidence that Nato is preparing for the long-haul.

Belgrade too can watch the weather and it is well aware of the forces that Nato has now mustered. Within days, the US aircraft carrier the Theodore Roosevelt will add its strike planes to Nato's attack force along with additional warships able to fire cruise missiles.

The Yugoslav President Slobodan Milosevic knows that some members of Nato - not least the Greeks - are uncertain about the air campaign. So far their resolve has nonetheless remained firm.

He may be hoping with this offer to weaken the Alliance's solidarity.