Instead of just champagne and speeches, the alliance partners will have to grapple with how to defeat Yugoslav President Slobodan Milosevic, get Serbian troops out of Kosovo and return all ethnic Albanian refugees to the province under international protection.

Before NATO's bombing campaign began, President Bill Clinton and other NATO leaders saw the summit as a chance to celebrate the cold war victory over the Soviet Union and to welcome the alliance's three newest members, Poland, Hungary and the Czech republic.

Now, with thousands of refugees from Kosovo homeless and the possibility that NATO could commit ground troops to combat for the first time if the situation worsens, state department officials said the atmosphere should be neither too upbeat nor too gloomy. Nonetheless, 50 years of accomplishments can't beignored, they say. Administration officials say a fly-by of NATO jets was considered but rejected because of Kosovo. The formal dinners, lunches and other diplomatic functions are expected to go on but there will be no black-tie events.

And they are calling the event a commemoration, not a celebration.

In addition to heads of state and foreign and defense ministers from the 19 NATO members, top officials from NATO's partnership for peace members, such as Austria and Uzbekistan, also are due to attend the April 23-25 conference. That would make it the largest assembly of foreign leaders in Washington since President Kennedy's funeral. There was supposed to be a session of the NATO-Russia permanent joint council, but US officials say the Russians have not said whether they will attend the summit or at what level. Russia has withdrawn its representative from NATO headquarters in Belgium. At their summit, the NATO leaders also plan to redefine the purpose of NATO for the 21st century in a new strategicdoctrine, the officials said.

Secretary of State Madeleine Albright said, ``The summit will focus simultaneously on what has been and is, and what will be ... including every aspect of the situation in Kosovo and the surrounding region.''