War in the Balkans: Analysis - Nato's big test: If the air war fails, is there a will to send in ground troops?

IT IS, surely, no longer a matter of if, but when they go in. For all the damage being inflicted on Serb installations by air strikes, and despite the opaque offers emanating from Belgrade, the plight of the refugees and the displaced deepens.

In this war it launched for humanitarian reasons, the West has a seemingly inescapable moral obligation to send in ground troops to provide the deliverance for the Kosovo Albanians it promised - but which its bombs could not deliver. With each image of suffering in the Balkans, the West's vision of how the war must end grows starker. Once a ceasefire would have done; now all Serb forces must be removed from Kosovo and not merely removed but eliminated as a military threat to Kosovo. Even as the bombing started, a deal with Slobodan Milosevic still seemed possible. Now there can be no compromise. He is to be overcome and - ideally - overthrown. The question is, how? There are no easy answers.

Until a few days ago governments in London, Washington and Paris assumed that whatever the revulsion at thetreatment of the ethnic Albanians, public opinion would not tolerate the casualties certain in a land war. That assumption may no longer be true. But thus far, ever-greater use of air power has been the chosen means. The targets are not only purely military; they include refineries, fuel depots, railways and bridges - soon radio and television facilities - the very sinews of a functioning country.

Nato commanders continue to hope this strategy will work, and say Tuesday's truce offer suggests Mr Milosevic is buckling. But the latest events suggest that may be just another case of wishful thinking.

The Milosevic mind may be hard to fathom but three strands run through it. One is the overriding goal of retaining power. Another is his constant tapping of Serb nationalism. The last is a willingness to do anything to achieve his ends.

Thus Serbia will not surrender Kosovo without a fight to the finish. No means to that end are ruled out: sealing borders, laying waste territory, the use of human shields to prevent attacks on Serb targets.

Like a desperate poker player, he keeps raising the stakes. If he cannot save himself by a deal, then there will not be a Kosovo worth saving either. Conceivably, a ground war could even lead to a Wagnerian finale in a bunker beneath Belgrade, the fate of the warmonger of 60 years ago to whom Mr Milosevic is constantly compared. Small wonder that Nato hesitates. The dilemma was unwittingly but perfectly encapsulated this week by the former prime minister John Major who, almost in the same breath, opposed a ground war yet criticised Nato for having ruled one out even before the bombing war had begun.

William Cohen, US Defense Secretary, again insisted Nato troops would not enter a "non-permissive environment." In fact, with two dozen Apache helicopters and thousands of US troops on their way to Albania, the alliance's pivotal member is edging towards doing exactly that. Public opinion, even in the US, looks readier to accept the inevitable human losses.

Even so, it may not yet fully appreciate the difficulties of timing, logistics and terrain - not to mention Nato unity - involved in a ground campaign are considerable.