Leading article: Slowly but surely we are nearing a ground war

IS THIS "mission creep"? The famous phrase from the Vietnam war has come back to haunt the leaders of the post-Vietnam generation. Are we witnessing a gradual, irresistible extension of the war aims in the Balkans, the kind of ratchet mechanism that drew the US into a massive land war which no one intended? Or is it bluff? Is Mr Blair's incremental but definite tightening of the terms of engagement in Kosovo designed to frighten Slobodan Milosevic into suing for peace? Or - a third possibility - is a ground war what Tony Blair intended all along, but could not admit to because the Nato partners would not wear it?

There is no doubt that, as Thomas Sutcliffe, our parliamentary observer, put it this week, the Government is engaged in a game of Grandmother's footsteps. Every time Grandmother turns around, the prospect of ground troops being deployed against the Serbian army seems to have crept closer, and yet nobody will admit to having moved.

But moved they have. Mr Blair began the war by promising that "there is no question of Nato ground forces being sent in unless it is to police an agreed political settlement". Three days later, he said that forces could go in with the refugees in order to "lead them back into their homes in Kosovo". On Monday this week, the wording became more active: "There will be an international military force that will go in to secure the land for the people to whom it belongs." And in the Commons on Wednesday he said: "The difficulties of a land force invasion of Kosovo against an undegraded Serb military machine are formidable." So, while Nato troops will not fight their way into Kosovo, they may yet drive in against a degraded military machine.

Whatever the reasons for this slow, much-denied shift in British, American and - by next week probably - Nato policy, it is to be welcomed. The deployment of ground forces should have been planned and threatened a year ago, but it is none the less essential now.

However, our leaders should be taking Britain and its Nato allies into this thing without creeping around the point. Ambiguity is hardly the right way to mobilise public opinion. Nor should the peoples of Nato countries be soft-soaped about the consequences of setting up a protectorate in Kosovo against Serbia's will. Suggestions from Nato that troops will be able to drive into Kosovo without opposition from a bombed-out and demoralised Serb army are wishful thinking.

Milosevic, in his propaganda counter-strike yesterday, said: "When our soldiers are dying, they know why they are dying. They are dying for their homeland, for their fatherland. And for what will your soldiers die, 5,000 miles from home?" Well, they will be dying to put an end to "ethnic cleansing", for a democratic, peaceful Europe.

But to defeat Serbs fighting for their fatherland will require leadership. Fighting a war by multinational committee, which is what Nato is, requiring a consensus among 19 nations, demands tact and diplomacy. But, just as Mr Blair has insisted that Milosevic does not have a veto on Nato action, nor should Greece. The Greeks may be Nato's weakest link, sympathetic to the cause of their traditional ally, orthodox Christian Serbia, but they will not leave Nato. Fortunately, Milosevic has so far acted in such a way as to keep Nato together, while Russia is unwilling to move beyond its stance of bellicose neutrality.

Nato's leaders must give a lead to their peoples this weekend. Public opinion is less of a constraint on Mr Blair than on any of his fellow leaders, and he is under more of an obligation to come clean. He should prepare us for a ground war not by stealth, but by saying clearly that British lives will have to be risked at some time soon. And he should come to Parliament and win a vote for it.