NOVI SAD, Yugoslavia (AP) _ Ice building up along the remains of three downed bridges that NATO blasted in its air campaign against Yugoslavia could cause the Danube River to freeze this winter and then flood in the spring, Hungarian officials warned Sunday.

Visiting the northern Yugoslav city of Novi Sad, the chairman of Hungary's Committee for the Environment, Zoltan Illes, urged the international community and the European Union to help clear war debris now clogging the 1,780-mile river.

Winter ice and a following spring thaw could swamp up to 600 square miles of land in Hungary, Illes said, endangering about 80,000 people there who live along the Danube.

``We need a minimum of 2-3 months to shift these objects, and we have to act now,'' Illes said after arriving in Bucharest, Romania, for a European symposium on religion, science and the environment.

George Zavvos, an expert from the European Commission, said at the symposium that the commission ``attaches great importance to the reopening of the Danube channel.''

Based on environmental damage already done, Zavvos said the committee estimated the river's cleanup cost at about $15 million. Another $10 million or so would be needed for ``temporary reconstruction of a bridge,'' he said.

However, Illes said it would cost just $1 million to shift the rubble and $3 million to remove it. Failure to do so could lead Hungary to spend up to $4 million itself in preventing an ice buildup.

The EU and other international groups should fund the cleanup, Illes said, and ignore sanctions against Yugoslavia intended to force Yugoslav President Slobodan Milosevic from power.

``The winter will come before Milosevic will go,'' Illes said.

But Yugoslav officials, whose country would also be affected if the Danube floods, said they doubted the river would freeze.

``Theoretically there is a problem, but you have to take into consideration the climate conditions and the level of the river,'' said Miroslav Spasojevic, a senior counselor for the Yugoslav Development Ministry.

Experts said that for ice to begin to pile up in the area, the water level has to be low, the weather must be cold enough, and at least half of the surface has to be frozen over.

The Danube has been at its lowest in more than a decade, down to almost 6 1/2 feet from the normal 13 feet.

With the Danube cut off, some countries upstream have lost the equivalent of millions of dollars in trade revenues. Yugoslavs have opened a detour channel, but they have not let vessels from countries that supported NATO's campaign use the bypass.