Enric Marti/AP Ethnic Albanian children from Kosovo reach out for bags of clothing being distributed by an Albanian aid agency at a refugee center in Tirana. Albania has taken in 300,000 Kosovo refugees in the last three weeks, the vast majority of them ethnic Albanians.

WASHINGTON (AP) - Pentagon leaders expressed regret yesterday that civilians were killed in a mistaken NATO attack on a refugee convoy in Kosovo, but seethed at the prospect of Yugoslav President Slobodan Milosevic using the deaths for propaganda gains.

"You cannot have this kind of conflict without some errors like this occurring," President Clinton said.

Defense Secretary William Cohen said the pilot was evading Serb anti-aircraft artillery and missile fire at the time and had to make a "split-second decision" when he spotted the convoy.

"It was under extraordinary circumstances with the kind of stress placed upon pilots," Cohen told the Senate Armed Services Committee in the first congressional hearing on the air war since it began March 24.

Clinton blamed Milosevic, saying the civilian deaths would not have occurred had the Yugoslav president not forced them from their homes and used them as human shields. He called the tragedy "inevitable," but said it was no reason to change the NATO mission.

"You cannot have this kind of conflict without some errors like this occurring," he told the American Society of Newspaper Editors in San Francisco. "This is not a business of perfection."

Clinton said NATO had no choice but to act against the ethnic cleansing.

"He is now determined to crush all resistance to his rule, even if it means turning Kosovo into a lifeless wasteland," Clinton said.

Cohen, testifying with Gen. Henry Shelton, chairman of the Joint Chiefs of Staff, before the Senate Armed Services Committee, said the Kosovo conflict may stretch into summer and emphasized that American casualties are likely. Many committee members expressed deep doubt that NATO can win without ground troops.

Sen. Bob Smith, R-N.H., a 2000 presidential contender, urged the administration to ask Congress for a declaration of war and said he would vote against it.

Evoking images of the Vietnam quagmire, Smith said this was the "Balkan swamp."

Cohen, facing the committee on which he sat during his years in the Senate, said the Clinton administration has no intention "for the present" to begin planning a land invasion.

Later, in an appearance before the House Armed Services Committee, Cohen said he had "not seen any evidence" that U.S. allies in NATO are interested in adding ground forces now or later.

In a presentation featuring colorful charts depicting NATO's air offensive, Shelton told the senators that "in the next few days," attacks would be carried out against the most sensitive targets on NATO's list. He said these targets were classified secret.