Several congressional Democrats and foreign policy experts praised President Clinton for yesterday's diplomatic breakthrough on Kosovo, but most Republican presidential candidates said the administration deserves no credit.

As Washington elites absorbed reports that Yugoslav President Slobodan Milosevic had made major concessions that could lead to peace largely on Western terms, many expressed concern that Yugoslav leaders may renege on the agreement. Full judgments, they said, cannot be rendered until it is clear that Serb-led troops actually have left the embattled region and refugees have been allowed to return safely.

Still, many Democrats said Clinton's commitment to NATO's air campaign appears to have been vindicated. "The president demonstrated the political leadership, courage and conviction to ensure that genocide and ethnic cleansing do not hide behind the international boundaries," said Sen. Joseph R. Biden Jr. (Del.), ranking Democrat on the Senate Foreign Relations Committee.

The sharpest criticisms came from GOP presidential contenders. Some criticized the president's leadership and said Clinton had made unacceptable compromises to gain a deal, while others questioned whether the bombing campaign should have been undertaken in the first place.

Elizabeth Dole said in a statement: "While I welcome any move by the Serbian regime toward a just and sustainable peace, the terms that Belgrade is now being offered are weaker than the president's previously stated demands. . . . It appears the Clinton-Gore administration may consider acceptance of a [peacekeeping] command structure that is not under NATO control."

The Belgrade agreement says a post-bombing international peace force would have "essential" or "fundamental" NATO participation, although the United Nations would authorize it. White House officials interpret that to mean that NATO and not the U.N. -- where Russia and China are powerful members -- will control the forces that would oversee the return of Kosovo refugees.

Texas Gov. George W. Bush (R) told reporters in Houston, "If in fact there is an agreement and it meets strong conditions, all Americans will be pleased that men and women won't be placed in harm's way." If U.S. peacekeeping forces enter Kosovo, Bush said, they should operate under U.S. or NATO command, and Clinton should specify a deadline for their withdrawal.

Among other GOP candidates, former vice president Dan Quayle said Clinton was forced to negotiate because of declining poll numbers and the prospect of a protracted conflict. "The Clinton administration squandered substantial resources and, far more importantly, our nation's credibility in the pursuit of matters wholly unrelated to America's vital national security interests," he said.

Patrick J. Buchanan said: "Does the Clinton administration deserve credit for the most powerful country in the world smashing a fifth-rate power that can't even defend itself? I think we ought to be ashamed of ourselves."

Rep. John R. Kasich (R-Ohio) said: "It sounds to me like a deal we should accept. But overall, I think that this Kosovo program has been a disaster."

Sen. John McCain (R-Ariz.), a presidential candidate who has prodded Clinton to prosecute the war more aggressively, said NATO should insist that all Yugoslav military and paramilitary forces have "withdrawn in good order, quickly, without committing any further atrocities" before suspending air operations. He questioned what the agreement means by allowing an "agreed number" of Yugoslav forces to return to Kosovo, suggesting that it was a loophole "big enough to drive an armored battalion through."

In Congress, reaction ranged from guarded optimism to deep skepticism. But Robert Kagan of the Carnegie Endowment for International Peace said that assuming the Serb-led troops withdraw as called for in the Belgrade agreement, "it's a huge victory for NATO, the United States. . . . It's a victory for Clinton and for McCain and the Republicans who supported him."

Staff writer Terry M. Neal contributed to this report.