As NATO planes hammered bridges, petroleum facilities and a power plant in Yugoslavia, the United States and its allies announced yesterday that they will airlift up to 100,000 ethnic Albanian refugees out of the embattled Balkans and offer them temporary shelter abroad.

U.S. officials emphasized that the initiative is not meant to resettle the more than 350,000 refugees from Kosovo permanently. NATO authorities repeatedly have vowed they will ensure that all ethnic Albanians who have been driven from Kosovo since the bombing began March 24 will be able to return to their homes under protection from an allied peacekeeping force.

But NATO spokesmen in Brussels said the United States has agreed to take 20,000 refugees -- with Germany accepting 40,000, Turkey 20,000, Norway 6,000 and Greece and Canada 5,000 each -- in an effort to ease the burden on overwhelmed authorities in Albania and Macedonia while the conflict rages on. Officials said no decision has been reached on where to put those getting U.S. help. But Pentagon authorities reported several military bases outside the United States are under consideration, including Guam and Guantanamo Bay, Cuba.

With NATO airstrikes in their 12th day, Yugoslav troops were reported to be shifting the focus of their own attacks in Kosovo, driving toward the province's mountains where secessionist guerrillas were said to be regrouping for what NATO's chief military spokesman said appeared to be a last stand.

Forecasters said the thick clouds over Yugoslavia that have obstructed alliance airstrikes would start clearing and NATO authorities predicted greater success in finding and hitting Yugoslav field forces. But to facilitate all-weather operations, the United States announced it is sending 24 Apache helicopter gunships and 18 missile launchers to Albania for use against tanks, armored personnel carriers and other Yugoslav military targets in Kosovo.

The Pentagon spokesman, Kenneth Bacon, disputed suggestions that dispatch of the Apaches -- along with 2,000 American soldiers to guard the combat group dubbed Task Force Hawk -- marked a first step toward expanding the NATO operation into a ground war. He called it "a logical expansion" of the air operation, reflecting the fact that the helicopters would be able to fly under the low clouds that have thwarted bombing runs by airplanes.

"It's to give us the type of tank-killing capability that the bad weather has denied us," Bacon said. "It will give us the capability to get up closer and personal to the [Yugoslav] units in Kosovo, and to do a more effective job at eliminating or neutralizing the forces on the ground."

Still, the units had not been envisioned in the battle plan put forward at the start of the operation by Gen. Wesley K. Clark, NATO's top military commander, and U.S. officials have spent several days weighing the risks of involving U.S. combat units much closer to the Kosovo frontline than aircrews stationed in Italy and elsewhere.

Even with the green light, Bacon said it could take seven to ten days for the helicopters and Multiple Launch Rocket Systems, armed with long-range Army Tactical Missile Systems, to reach Albania. He noted the complexities of trying to sequence flights carrying the soldiers and equipment with the airlift of food, tents, blankets, clothing and other humanitarian assistance also being organized for the flood of refugees into Albania and Macedonia.

Several prominent congressional Republicans and Democrats urged the administration to embrace the option of an invading ground force, citing the air campaign's failure so far to compel Yugoslav President Slobodan Milosevic to accept a U.S.-drafted peace accord and withdraw his forces from Kosovo, the southernmost province of Serbia, which is the Yugoslav federation's dominant republic.

"The diplomacy won't start until our president stops saying no ground troops," declared Sen. Richard G. Lugar (R-Ind.), chairman of the Senate Foreign Relations Committee. Democratic Sens. Charles S. Robb of Virginia and Joseph R. Biden Jr. of Delaware also urged Clinton to revive the possibility of deploying U.S. forces in Kosovo.

U.S. and NATO authorities continued to insist they have no intention of sending ground troops into Kosovo. But the ranks of NATO ground troops on the edges of the battle zone have begun to rise, not only by the addition of the Apache helicopter task force, but also by troops dispatched to deal with the refugee crisis.

As many as 8,000 troops from Italy and other NATO countries are being sent to Albania to help set up six refugee camps and ferry food and water to refugees at the border. Another 12,000 British, French and German soldiers, already in Macedonia as lead elements of a planned NATO peacekeeping force, also are being enlisted to perform similar humanitarian tasks.

NATO forces stationed in Bosnia as peacekeepers, meanwhile, indirectly entered the fray Saturday by blowing up a railroad track that passes through Bosnia on the way from Serbia to the other Yugoslav republic, Montenegro.

A U.S. spokesman explained the peacekeepers were within their mandate because they were trying to keep Bosnia safe and secure from Yugoslav troops, who he said intended to use that route to Montenegro.

In what NATO authorities described as a stepped-up effort to raise the price for Milosevic of his continued crackdown on Kosovo, alliance forces attacked a police academy in Belgrade Saturday night, as well as a heating plant and petroleum depots. Outside the Yugoslav capital, NATO airstrikes also hit highway bridges and an ammunition plant.

In Novi Sad, Serbia's second-largest city, NATO strikes destroyed the Freedom Bridge across the Danube River. It was the second bridge hit there this week, leaving one and prompting people to resort to boat crossings.

Yugoslav government-controlled media said at least three people, including an elderly woman, were killed and 21 injured in the attack. Another two were reported killed in the attack on an oil refinery at Pancevo.

But NATO officials made no apologies, saying the widening strikes on dual-use facilities, like power plants and bridges, that serve civilian as well as military needs are critical to choking Yugoslav military operations in Kosovo and increasing the pressure on Milosevic.

"This isn't a cricket match," Air Commodore David Wilby, NATO's chief military spokesman, told reporters in Brussels. "Taking those bridges down is causing immense inconvenience to the Serbian units that are trying to resupply their forces down in the heart of Kosovo."

Britain's Air Marshall John Day, briefing reporters in London, urged Milosevic and his principal advisers to "reflect on the even higher price which they are about to pay."

Nonetheless, there were signs the bombing may be having the unintended effect of rallying the Yugoslavs not against their leadership but against NATO. A large group of young people, many of them sporting targets on their chests, linked arms on one of the remaining bridges near Belgrade, in an attempt to symbolically shield it from destruction.

The bombing campaign "only increases our resolve to continue defending our country," Vladislav Jovanovic, Yugoslavia's ambassador to the United Nations, told Fox News. "Whoever tries to take Kosovo from us should count on our resistance to the very end."

Also on U.S. television, an aide to Milosevic decried the bombing of what he described as civilian targets. Belgrade's deputy mayor, Milan Bozic, who also is a federal minister in Milosevic's cabinet, said in an interview on CNN's "Late Edition" that NATO has created a "humanitarian catastrophe here in the very downtown of Belgrade." He struck a similar theme on ABC's "This Week," saying that, as he was giving the interview, the city was "under air alert," power plants were burning, and "the people are in shelters."

Bozic also reported on the three U.S. soldiers captured last week while on patrol along the border between Yugoslavia and Macedonia. Despite an earlier government announcement, he said the three will not be put on trial and will get a visit from Red Cross representatives within days. He branded earlier reports that the three would be given a military trial as "malevolent communication" by western journalists.

However, Jovanovic was more equivocal about the possibility of a trial, saying that an "investigation on the infiltration of Yugoslavia is underway. On the result of that investigation would depend whether there will be or will not be a trial before the military court."

In the field, the Yugoslav military turned its attention to routing remaining elements of the rebel Kosovo Liberation Army. Late last week, U.S. intelligence sources predicted that Yugoslav forces were close to snuffing out lingering resistance by the ethnic Albanian guerrillas, and NATO authorities said a final fight appeared to be shaping up in a southwestern mountainous region near the border with Albania.

"This is the last area where the [rebels] will be able to mount a serious resistance," Wilby said.

Despite the pledge by the United States and allied governments to provide temporary shelter for the Kosovo refugees, NATO officials said they are powerless to assist the hundreds of thousands of displaced ethnic Albanians inside Kosovo. Alliance authorities have ruled out any food drops to masses of refugees said to be concentrated in Kosovo's Pagarusa Valley or in the Yugoslav republic of Montenegro, worried such supplies could fall into the hands of the military.

Answering a growing chorus of criticism about the slow pace of the bombing campaign and the mounting refugee crisis, administration officials insisted the NATO operation is seriously eroding Yugoslav military capabilities. Speaking on NBC's "Meet the Press," Secretary of State Madeleine K. Albright rejected allegations that NATO was unprepared to deal with the refugee crisis, pointing to stocks of food positioned in the region ahead of the air operation.

"We were not surprised but we are appalled at the level of cruelty and barbarism perpetrated by Milosevic," she said.

Correspondent Anne Swardson in Brussels contributed to this report.

DEVELOPMENTS IN KOSOVO

* NATO forces stepped up their attacks, hitting an army headquarters, oil refineries and other targets near Belgrade. Yugoslav forces, meanwhile, were reported to be moving toward Kosovo's western mountains where ethnic Albanian guerrillas were regrouping for what NATO's chief military spokesman called a last stand.

* Western nations and relief agencies struggled to help the refugees as Albania reported that more than 31,000 people entered the country. Evacuation of some of the more 100,000 refugees in Macedonia began by air as NATO spokesman Jamie Shea said that several allied nations -- Germany, the United States, Turkey, Norway, Greece and Canada -- had offered to take in some refugees temporarily.

* The 55-nation Organization for Security and Cooperation in Europe said that Western monitors had spotted about 10,600 refugees on a mountainside near Qafa e Prushit, an almost inaccessible and rarely used border crossing between Yugoslavia and Albania.

* In Belgrade, the airstrikes are beginning to take their toll on the Yugoslav economy and its residents. The government has told state workers that it will not be able to pay them their latest salaries. Gasoline is scarce, food stocks are dwindling, and telephone service has been knocked out in some parts of the country.

* The United States said it is sending 24 Apache attack helicopters and long-range artillery units to take up positions in Albania for use against tanks, armored personnel carriers and other Yugoslav military targets in Kosovo. An estimated 2,000 troops will also be sent to operate and maintain the equipment, the Pentagon said.

* In the Montenegrin capital, Podgorica, about 10,000 Montenegrins demonstrated in the biggest outpouring yet of anti-NATO sentiment in the smaller of the two Yugoslav republics.

On the Edge of War

Although national security officials continue to rule out the use of ground troops, more and more U.S. and NATO troops are to be sent to areas on the outskirts of Kosovo.

9,800 U.S. troops were in the international peacekeeping force in Bosnia last week. That number is larger than usual because of a scheduled rotation of forces.

8,000 NATO troops are headed to Albania to aid refugee relief efforts.

2,000 U.S. troops are being sent to operate and maintain the Apache attack helicopters and long-range cruise missile systems ordered to Albania.

350 U.S. troops are in Macedonia conducting reconnaissance for the 12,000 NATO peacekeepers.

24 U.S. Marines are headed to Albania and Macedonia to assess the humanitarian situation.

12,000 NATO troops (mostly British, French and German) are in Macedonia to help with the refugee crisis.

SOURCE: NATO