''The intent of the amendment is to restore congressional oversight over the Kosovo mission,'' said Senator Robert C. Byrd of West Virginia, the provision's chief Democratic sponsor. ''Of course, the administration doesn't like it. They want a free hand to participate in military adventurism whenever and wherever they please. They don't want to hear a peep out of Congress.''

But critics said imposing an arbitrary deadline for withdrawal would send a dangerous signal of uncertain American resolve to President Slobodan Milosevic of Yugoslavia, and undermine the unity and morale of NATO's peacekeeping operation, which involves forces from Britain, France, Germany, Italy and other nations, in and out of Europe. They are trying to calm Kosovo in the aftermath of NATO's bombing of Yugoslavia early last year, when NATO acted to protect Albanians in the province.

A deadline ''would precipitate a year of dangerous uncertainty and wavering commitment to our allies,'' said Senator Carl Levin, Democrat of Michigan, a leading foe of the provision and sponsor of the amendment to kill it.

The 15 Republicans joined 38 Democrats in supporting Mr. Levin's decisive amendment, while 40 Republicans and 7 Democrats opposed it.

Mr. Levin's measure also eliminated a second provision to withhold 25 percent of the military's funds in Kosovo this year, unless Mr. Clinton certified by July 15 that the European allies were meeting their commitments for reconstruction aid, police officers and food and medicines. Without that certification, the measure required that money could be spent in Kosovo only for an orderly withdrawal of American forces.

The defeated provision's chief Republican author, Senator John W. Warner of Virginia, the chairman of the Armed Services Committee, remained undaunted. He vowed to offer the provision on the European share of aid as an amendment to the Pentagon's budget bill for fiscal year 2001 when that reaches the Senate floor.

On Wednesday, the House approved, by a vote of 264 to 153, an amendment on the European aid share similar to the Senate's. But the House version gives the next president until April 1, 2001, nearly nine months longer than the Senate, to certify that the European allies are meeting their commitments.