BELGRADE, Yugoslavia (AP) -Nearly a month after Yugoslav forces captured three U.S. soldiers along a disputed border, the Red Cross finally was allowed to see the men but chances of their release anytime soon were considered slim.

Western officials cited critical comments by a Yugoslav leader, meanwhile, as evidence of the first crack in President Slobodan Milosevic's regime since the NATO air campaign in Kosovo began March 24.

The U.N. relief agency said it had credible evidence Serb forces were using Kosovo refugees as human shields to help protect them from NATO airstrikes. And NATO said its anti-tank Apache helicopter force was ready to begin operations from neighboring Albania.

The European Union tightened economic sanctions and banned fuel shipments to Yugoslavia but left the touchy issue of enforcing it with an Adriatic naval blockade to be worked out by the NATO alliance.

International Committee of the Red Cross chief Cornelio Sommaruga gave no information about the soldiers' condition but said a Red Cross doctor and a delegate would pay another visit to the three soldiers Tuesday. After meeting Milosevic, though, he expressed pessimism they would be freed before the war ends.

"International humanitarian law says prisoners of war would be liberated at the end of active hostilities. Regrettably, we are not at this point at the moment,'' Sommaruga said.

The U.S. soldiers were shown on Serb TV after their March 31 capture near the Macedonia border with bruised faces and cuts. The Red Cross repeatedly had been denied access to the soldiers, who are believed held in or near Belgrade.

"I was able to talk to them only a few minutes,'' Sommaruga said at a news conference. "We looked into each other's eyes and shook hands very warmly.''

Sommaruga said, "it was not possible to have a full-fledged ICRC visit in accord with the provisions of the Geneva Convention'' but that he had given the men letters from their families and paper to write back.

White House spokesman Joe Lockhart said yesterday's meeting came "25 days late'' and represented a "bare minimum'' of what international law requires in terms of access to war captives. He said the three "appear to be in good condition.''

Held captive are Staff Sgt. Andrew A. Ramirez, 24, of Los Angeles; Spc. Steven M. Gonzales, 21, of Huntsville, Texas; and Staff Sgt. Christopher J. Stone, 25, of Smiths Creek, Mich.

When told the Red Cross had seen his son, Stone's father, Jim C. Stone of Avoca, Mich., said ''Yippee! That's absolutely wonderful news.''

Stone's mother-in-law, Lisa McKinney of San Antonio, Texas, said: ''At least we know he's alive.''

Sommaruga also said the ICRC would work to reopen its mission in Kosovo after receiving security assurances from Milosevic.

Yesterday afternoon, air raid alerts sounded in Novi Sad and Nis, Yugoslavia's second- and third-largest cities, signaling NATO attacks. After sunset, air raid sirens sounded in the central industrial town of Cacak.

NATO missiles blasted an already damaged bridge over the Danube River earlier in the day, sending the last of three rail and road crossings in Novi Sad crashing into the water.

NATO said it was destroying the bridges in the northern city to prevent troop deployments south to Kosovo.

Western officials said there were signs the air campaign was succeeding in demoralizing Serb resistance. They cited remarks by Yugoslavia's deputy premier, Vuk Draskovic, who called on Yugoslav leaders to ''stop lying to the people in Serbia, and finally tell them the truth.''

Draskovic, once the main opposition leader before joining Milosevic's government last year, said Serbia has been seriously weakened by the allied bombardment.

''They must say what will be left of Serbia in 20 days if the bombing continues,'' Draskovic said, telling CNN the Serb leadership must acknowledge that ''we cannot defeat NATO'' and ''we must respect this reality.''

In separate comments to reporters later yesterday, Draskovic also said his government was ready to accept a peace deal calling for a U.N. presence that would include NATO countries. Allied terms for peace include a peacekeeping force, an end to atrocities, autonomy for Kosovo and the return of all ethnic Albanian refugees.

Draskovic's statements do not necessarily reflect those of Milosevic's, but Western officials say his comments could signal a rift.

In a reflection of the political turmoil in Belgrade, Draskovic claimed the Yugoslav army took over the private Belgrade TV station owned by Draskovic's party after it aired earlier remarks critical of the government.

Later, however, the station returned to normal programming. Representatives of Studio B and other private stations said they jointly agreed last night to broadcast state television newscasts because Serbian TV was damaged earlier in the week by NATO airstrikes.

In Washington, State Department spokesman James P. Rubin hailed as a ''recognition of reality'' the comments by Draskovic.

''It remains to be seen as to whether he will be allowed to continue to tell the truth,'' British Defense Secretary George Robertson said. ''I think it shows that inside the system the facade of unity is cracking wide open.''

Democratic party leader Zoran Djindjic voiced skepticism about Draskovic's defiance of Milosevic, telling the German TV station ZDF: ''It's a role in a play written by Milosevic.''

An ethnic Albanian rebel commander, contacted by satellite telephone from Austria, said NATO attacks were having a serious impact on Serb forces in Kosovo.

The commander, Ramush Haradinaj, said Serb troops are now hiding in villages where NATO knows ethnic refugees are staying, forcing the civilians into basements while taking over the rest of the houses.

NATO's ability to attack Serb forces in Kosovo is expected to be bolstered once U.S. Army Apache attack helicopters go into action.

NATO military spokesman Col. Konrad Freytag said the ''full package'' of the Apache force is now in Albania, including supporting ground-based rocket launchers.

Refugees continued to flow out of Kosovo, with 3,000 crossing yesterday into Macedonia.

Most arrived by train and were put in a transit camp near the no man's land between Macedonia and Yugoslavia. More than 600,000 refugees have fled Kosovo over the past month.

UNHCR spokesman Kris Janowski said reports of refugees being used as human shields ''have substantial foundation.''

Kosovo had a prewar population of 2 million; more than 2,000 were killed in the Yugoslav crackdown that began in February 1998 until NATO took action.