Ethnic Albanian rebels, whom Yugoslav President Slobodan Milosevic often said he could eradicate in five to seven days of no-holds-barred war, have emerged after 73 days with larger numbers, more weapons and more entrenched bases in Albania. They seek an independence that neither Washington nor its allies support.

With Serb forces badly battered and apparently on their way out of the province, the Kosovo Liberation Army (KLA) has pocketed most of the gains it hoped to buy with its agreement to limited "autonomy" in the peace accord drawn up by the West, and rejected by the Serbs, in February.

"We are going to have a massive KLA problem," said a U.S. official who has been more sympathetic to the rebels than most of his peers. "If they are not disarmed and go around trying to settle scores with Serbs, it's going to be tough."

At the Pentagon, one planner said the threat to NATO peacekeepers would come in stages. In the beginning, angry Serbs might try to inflict enough casualties to induce the troops to leave. "As time wears on, and autonomy but not independence comes, it reverses. It becomes the KLA that takes action."

The scope of the U.S. Balkan commitment is far broader and deeper than Kosovo alone. President Clinton, with help from Secretary of State Madeleine K. Albright, has fashioned a program that would stretch well beyond his presidency and complete the overturning of a long-standing U.S. and NATO strategy in southeastern Europe.

For decades NATO has insulated itself from the turmoils of its Balkan flank. Albright proposed a substitute ambition--to open Europe's doors to the Balkans. The United States and NATO should do more than broker, and if need be impose, a settlement of Yugoslavia's ethnic wars. They should usher Yugoslavia and its neighbors into the same economic and military ties that bind central and northeastern Europe to the West.

In a three-page confidential memo to Clinton in April, Albright foresaw "a rebuilt Kosovo and a post-Milosevic Serbia," but her ambitions actually were greater. For southeastern Europe as a whole, the United States and the European Union "need to play a catalytic role in helping them develop their economies, their civil societies, their democratic infrastructure and their security relations," she wrote. "And we need to condition such help, as we did fifty years ago in Western Europe, on close cooperation among the beneficiaries and new understandings of sovereignty."

Senior White House officials said Clinton has now accepted that the Balkans and their neighbors are "a kind of cancer in the middle of Europe," and that consolidating Europe's prosperity requires a cure. Not only would a stable Balkans stabilize Europe as a whole, said one top official, but "a major flashpoint between the West and Russia will have gone away."

"We are going to stay engaged in this until this part of Europe looks like the rest of Europe," one senior State Department official said. "We're not talking about troops for two years. We're talking about a long-run engagement in the region."

That strikes critics as extravagance.

"Just as the Clinton administration decided it had to intervene in Kosovo to protect its investment in Bosnia, now it may have to intervene in Macedonia and Albania to protect its investment in Kosovo, and that may extend to Serbia as well," said Michael E. Mandelbaum, a professor at Johns Hopkins University. "We own the Balkans. NATO is now in the position of a real estate investor who keeps buying properties where the taxes exceed the rent."

By that analogy, administration officials said, the Balkans are a turnaround play. And European leaders see it in their interest to pay the bulk of the cost.

An aid program discussed last week by European leaders would entail investing as much as $30 billion over the next five years in Kosovo's neighbors--Macedonia, Albania, Bulgaria and Hungary--all of which suffered war damage to their economies.

"Huge financial assistance is going to be needed, and it's very clear to me that Europe is committed to rebuilding south Europe," said Rory O'Sullivan, who directs the World Bank's regional headquarters in Sarajevo, Bosnia. He noted that Romano Prodi, a former Italian prime minister who is the incoming head of the European Commission, has expressed enthusiasm for the project.

Many experts say it would be a mistake to view the West's newfound interest in strictly economic terms, however, because the aid now being planned will be accompanied by an infusion of Western expertise and a variety of demands that will help liberalize the region's antiquated economic and political structures. The carrots being dangled include eventual membership in the European Union and possibly NATO itself.

The trouble with plans for integration is the same Belgrade regime that prompted them. If the war leaves Milosevic in power, Yugoslavia will be "the economic black hole of the region," said one European diplomat, leaving its leaders angry and willing to foment additional trouble as a means of gaining leverage and Western concessions--a technique they used with some success in Bosnia.

"This is not a durable solution," said Carlos Westendorp, the senior Western civilian in Bosnia, "if he retains the capability of destabilizing other provinces and republics."

CAPTION: The return of ethnic Albanian refugees to the province of Kosovo is but one problem facing the United States and its NATO allies after their apparent victory in Yugoslavia.