As President Clinton wound up a daylong celebration of his administration's brightest military achievement here today, strange, troubling rumors began trickling in.

Russian troops were driving toward Kosovo and perhaps were planning to enter the war-torn province before NATO's own peacekeepers could take up positions there, according to reports from Yugoslavia. The accounts threatened to knock the legs from Clinton's victory lap because NATO and Moscow had yet to agree on how and when Russian troops would participate in the international security force planning to enter Kosovo.

But Clinton and his aides dismissed the talk, saying they had assurances from Russian Foreign Minister Igor Ivanov that no such thing was happening. Even after Clinton returned to Washington and sat down for a live evening interview with public television's Jim Lehrer, he said the Russian soldiers apparently were "just prepositioning," and there was no cause for alarm.

A few hours later, however, chagrined administration officials were confronted with CNN footage of Russian armored personnel vehicles snaking through cheering crowds in Pristina, Kosovo's capital. The surprise sent White House and Pentagon officials scrambling to determine what had gone wrong and to revise their earlier statements.

A little after 9 p.m., White House press secretary Joe Lockhart announced that "the Russians assured us that they did not intend to deploy in Kosovo before" NATO peacekeepers could enter the province. "As Foreign Minister Ivanov has said, it was an unfortunate mistake, and the Russian troops will be withdrawn immediately." Ivanov delivered his comments in a CNN interview.

Privately, administration officials said the incident apparently stemmed from a communications breakdown -- or a battle of wills -- between Moscow's government and its military officers in Bosnia, where the Russians are part of an international security force. "When Ivanov found out about it, he was as surprised as we were," said one senior official.

"Clearly there's some confusion within the Russian government, and they will be sorting out within their government how this happened, just as we will work with them on how we proceed from here regarding arrangements for the peacekeeping force," another administration official told Reuters. "If they follow through and the troops leave immediately, then we understand that mistakes do happen. If that doesn't happen, then obviously it's a different situation."

Knight-Ridder, however, quoted an administration source as saying the Russian midnight march had shocked U.S. officials. "Either it was a renegade force or they had been lying to us all day," the official said of the Russians. "And you have to wonder whether they're going to be able to just turn around and easily leave."

Adding to the confusion was the Russian news service Interfax, which cited military and diplomatic sources in reporting that Moscow "sanctioned" the move.

U.S. military officials in Europe expressed amazement at the Russian troops' movement and said they had no clear indication of what their intentions were. At the Pentagon, senior military officials were following the news on CNN, trying to determine the size and nature of the Russian force.

The Pentagon appeared more concerned that blame for the invasion lay in the souring state of military-civilian relations in Moscow than in the possibility that the Yugoslav and Russian governments had made plans behind its back.

The Russian incursion darkened an otherwise lustrous day for Clinton, who saluted U.S. military personnel at this northwest Missouri base that is home to the B-2 stealth bomber, which won rave reviews for its inaugural combat missions in Yugoslavia.

Clinton said the U.S. military community's example of tolerance and morality -- more than its bombs -- forced Yugoslav President Slobodan Milosevic to agree to peace on NATO's terms. But Clinton also indulged in a moment of self-satisfaction over his often-criticized policy of using airstrikes alone to attack Serb targets.

"As you know," he told several hundred people gathered in a hangar, "everybody in America was free to tell me I was wrong about this from the get-go."

The president wasted no time in beginning to shape the conflict's history in sweeping images of a moral, diverse force overcoming an evil, intolerant despot.

Throughout the 78-day war, Clinton said it was imperative to halt Milosevic's policy of atrocities against a people "because they had a different color skin, because they had a different ethnic background, because they worshiped God in a different way." Today, he modified that dynamic, saying NATO and the U.S. military prevailed precisely because they embrace diversity among people and nations.

"You helped to put the lie to Mr. Milosevic's campaign of ethnic cleansing and killing . . . by the power of your example," Clinton said in his 27-minute speech. "And make no mistake about it, it is even more powerful than the power of your bombs."

He described their "example" as "a reaffirmation of the moral worth, and the sheer joy, of working together as equal human beings for a good cause." Milosevic was unable to divide NATO and win the war, Clinton said, "because we had made a decision as a free people to respect the inherent dignity of every person, to give everybody a chance, to learn from people who are different, to be on the same team."

Staff writer Dana Priest in Washington contributed to this report.

CAPTION: President Clinton addresses a gathering of Air Force personnel and their families in a hangar at Whiteman Air Force Base, Mo., home of the B-2 stealth bombers that made their combat debut during the attacks on Yugoslavia.