Rejecting President Milosevic's offer for a unilateral ceasefire in Kosovo, to honour the Orthodox Easter this weekend was relatively easy for NATO. Even if the Yugoslav troops do adhere to the ceasefire, the paramilitary formations now terrorising local Albanians will continue their offensive.

A similar technique was employed in Bosnia earlier this decade, when innumerable cease-fires were declared, only to be breached. Furthermore, the idea that Milosevic deserves a respite for Easter is obscene: it is tantamount to saying that, on account of a Christian holy day, NATO should cease trying to offer protection to European Muslims who are being massacred because of their religion and ethnic affiliation.

But the main question now is what precisely NATO wants, and what offer from Milosevic will be considered genuine and substantial enough in order to warrant even a temporary cessation of hostilities. The simple answer is that NATO does not have an answer; much will depend on when the offer for a settlement comes, but also how it is packaged.

The alliance has to take into account a whole host of political and strategic constraints. The horrific pictures from Kosovo have increased public demands to identify Milosevic as a suspected war criminal. Governments have resisted this temptation partly because they have doubts about the legal basis for identifying a head of state which is still a member of the United Nations as a war criminal, and partly because they suspect that they may yet have to deal with Milosevic across a negotiating table.

However, if the violence continues the pressure to indict the Yugoslav leader may become irresistible. Just as importantly, the alliance has to bear in mind the fact that, the moment air strikes are suspended, even on a temporary basis, it would be very difficult to restart them. The doubts about the efficiency of air strikes will intensify and NATO will not be able to avoid a debate in the UN Security Council about the mandate for the operation.

In presentational terms, therefore, the alliance must be sure that when it does sit down with Milosevic the talks will result in a settlement which can be safely presented as a Western triumph, and which can offer reasonable guarantees that air strikes will no longer be needed. But, even assuming that these political hurdles are met, what precisely will the alliance demand from Yugoslavia? Officially, the conditions for a settlement have not changed: Milosevic must accept a complete withdrawal of his forces from the province, the return of all refugees, an autonomy for the province of Kosovo and the presence of an international force designed to police the deal for a number of years.

In practice, however, all NATO military planners know that these claims are basically irrelevant. There is no chance that Milosevic will simply accept all these conditions at the same time; this is tantamount to asking him to commit suicide. And the idea that the Kosovo Albanians would ever consent to return home in exchange for a promise of autonomy within the country whose government has tried to murder them wholesale is plainly idiotic.

But the alliance is stuck with this package mainly because it cannot admit openly that the final outcome is an independent Kosovo, since this could upset most of the other countries in the Balkans.

In order to avoid a stalemate, NATO is now tilting towards a new negotiating stance. Is it based on what may be called "front-loading": demanding from Milosevic acceptance of enough conditions even before the serious peace negotiations begin, in order to make sure that, whatever happens, the alliance will gain a foothold with its ground troops in Kosovo, and therefore retain the initiative.

The shift in Brussels is unmistakable. The return of refugees under the protection of Western forces is now the minimum precondition. According to alliance spokesmen this can take place irrespective of whether a peace treaty has been signed; the essential element is that this return of refugees will take place under Western military supervision, a nicer way of saying that Milosevic has to agree to the introduction of NATO troops on his territory even before the negotiations begin.

If Yugoslavia agrees, the air strikes will stop the moment the first convoys of Western forces cross the frontier. If not, almost anything else Milosevic may offer will be rejected as mere window-dressing. The Yugoslav leader has spent a decade selling fake peace plans in Europe. He is now about to pay heavily for his record of deceit.

Jonathan Eyal is Director of Studies at the Royal United Services Institute in London