Defense Secretary William S. Cohen yesterday called NATO's air campaign against Yugoslavia "the most precise application of air power in history," but insisted the operation should not be taken as a sign the United States was likely to rely more on warplanes to win future conflicts.

Responding to weeks of criticism that the air operation was poorly conceived and violated basic military doctrine by using only air power and applying force incrementally, Cohen defended the 11-week campaign as ultimately effective and the only military option that NATO allies would accept.

At a Pentagon news conference filled with questions about the long-term lessons of the war, Cohen said the extensive damage done to Yugoslav military assets -- with relatively few civilian casualties and no NATO combat fatalities -- vindicated the alliance's approach of fighting "with patience, with persistence and with great precision."

But he cautioned against drawing overly broad conclusions about the future use of U.S. military power. He said the alliance's reluctance to mount a land invasion should not be read as a general hesitation about committing ground forces or as a lessening in Pentagon support for maintaining a strong Army.

"Air power, in this particular case, has been effective and has been successful," Cohen said. But "it should not be seen as the only course of military combat in the future."

Many retired military officers and other defense experts have faulted the Clinton administration for allowing NATO to take the ground option off the table at the start of the campaign. Critics contend that, by maintaining at least the threat of an invasion and also attacking more aggressively from the air at the outset, NATO could have ended the conflict sooner and minimized the suffering of ethnic Albanians in Kosovo. Instead, NATO members, squeamish about launching NATO's first war, gambled wrongly that limited strikes would bring a quick capitulation by Yugoslav President Slobodan Milosevic.

"We are not afraid to use, in any case, a ground component to a military campaign," Cohen said. "This was the best of a series of bad options -- this was the best option under the circumstances -- and ultimately it has proved successful."

Gen. Henry H. Shelton, chairman of the Joint Chiefs of Staff, who appeared with Cohen, said that even if NATO had agreed to mount a ground war, the air campaign would have lasted at least as long as it did -- and possibly longer -- to prepare the way for sending land forces into Kosovo.

"This campaign has unfolded not in exactly the way we might have fought an air campaign, had we been fighting unilaterally," said Shelton of an operation jointly planned and directed by the 19 NATO members. But he added that it "has been very effective."

Still, much of the impact of the airstrikes, particularly against Yugoslav forces in Kosovo, came only in the final two weeks of the operation. This was confirmed in a chart that Shelton displayed showing large numbers of Yugoslav armored vehicles and artillery in Kosovo being destroyed only after the 67th day of the 79-day conflict.

By then, the cloud cover that had hampered operations in the first two months had largely lifted and NATO's fleet of warplanes had swelled to nearly three times the 400 involved at the start, allowing continuous attacks on Yugoslavia from all directions. A major offensive by reinvigorated Kosovo Liberation Army rebels, who tried opening a second corridor into southwestern Kosovo from Albania, also aided NATO forces by flushing Yugoslav troops into the open.

By the end, Shelton said NATO had struck 120 Yugoslav tanks, 220 armored personnel carriers and 450 artillery and mortars in Kosovo. He said 60 percent of the facilities of the 3rd Army -- the main occupying force in the embattled province -- had been destroyed, as had 35 percent of the 1st Army's facilities and 20 percent of the 2nd Army's.

CAPTION: Defense Secretary William S. Cohen and Gen. Henry H. Shelton, head of the Joint Chiefs of Staff, defend NATO strategy in Balkans at news conference.