SLOBODAN MILOSEVIC'S army has demonstrated an ability to move people quickly when it wants. Using murder, rape and beatings as motivators, his soldiers forced hundreds of thousands of civilians out of their homes and out of Kosovo in a matter of days. So now, if his generals suggest that they need more time to pull their own troops out of Kosovo, NATO need show no sympathy. Until Mr. Milosevic complies in full with the peace agreement he has signed, NATO should intensify its bombing of Yugoslav forces and continue mobilizing ground troops along Kosovo's borders.

It's impossible to know for sure what motivated Yugoslavia's latest recalcitrance. Maybe Mr. Milosevic thinks he can win a more favorable deal by exploiting differences between the Kosovo Liberation Army and NATO, between NATO and Russia or among NATO members. Maybe his generals, or some faction of them, don't like the deal. It's also possible, though, that the argument is more about sequencing than actual implementation. Before they withdraw, Yugoslav generals want to make sure that the U.N. Security Council will authorize a peacekeeping force to replace them -- and to keep the KLA from taking over. For such a resolution to pass, both Russia and China have to be on board.

So the United States is right to go on talking -- with the Russians and Chinese, with NATO allies, with Yugoslav generals if they have something to say. There's nothing wrong, either, with pursuing diplomacy at the United Nations; if the Security Council will approve NATO's rescue operation, so much the better.

But certain principles can't be compromised. The international peacekeeping force must have NATO at its core and a NATO general at its command -- not an official of the United Nations, the European Union, the Organization for Security and Cooperation in Europe or anybody else. Yugoslav forces must withdraw quickly -- all Yugoslav forces -- and NATO must do whatever it can to ensure that those forces commit no more atrocities as they retreat.

These conditions don't just have moral weight in light of the war crimes committed by Mr. Milosevic and his troops. They are also, as a practical matter, the minimum that will persuade Kosovo's deportees to go home. Until they are agreed to and implemented, the United States and its allies must maintain the strategy that has brought them this close to prevailing. The key factors of that strategy are NATO bombing, NATO unity, KLA pressure and the threat of NATO action on the ground.