Already Grim Outlook for Balkans Worsening : Relief: Disease and starvation threaten millions in the war zones of the ex-Yugoslav federation, officials warn.

Violence and deprivation are spreading throughout the war zones of the former Yugoslav republics and worsening an already dire outlook for millions of civilians at risk of death by starvation or disease this winter, U.N. and aid agency officials warned Thursday.

Security and living conditions have deteriorated rapidly in recent days in Bosnia-Herzegovina following the collapse of U.N.-mediated peace talks, and in Croatia due to a looming armed showdown between government and rebel Serb forces.

The decline has been aided by outbreaks of tension in Somalia, in the former Soviet republics and in Haiti, which have distracted the international community’s attention from the Balkan crisis at a time when relief officials say redoubled efforts are needed to avert a catastrophe.

The U.N. high commissioner for refugees, Sadako Ogata, has warned that Western inattention could contribute to the widespread misery expected in the coming cold months. She appealed this week for another $700 million in donations for the 4 million people in former Yugoslav republics that are now dependent on foreign aid for their food and shelter.

“The aid pipeline is precarious because of a certain amount of donor fatigue,” said UNHCR spokesman Peter Kessler, noting a sharp drop in pledges from Western countries. “We are having to compete with other crises like those in Somalia and the Caucasus.”

The World Health Organization also warned this week that most hospitals in the conflict areas of Bosnia and Croatia are in disastrous condition, and that those living in besieged cities such as Sarajevo face a skyrocketing risk of epidemics because of the lack of water, heat and adequate nutrition.

In the two weeks since Bosnia’s Muslim-led Parliament rejected a plan that would have carved up the republic into three ethnic mini-states, U.N. observers say the combatants have become more strident in their campaigns to take territory and to thwart humanitarian aid.

The International Committee of the Red Cross had to postpone a massive Croat-Muslim prisoner exchange that had been expected to start Thursday because of new procedural demands made by the Bosnian Croats, said Red Cross spokeswoman Jette Sorensen.

Two major U.N.-escorted convoys trying to bring food and medicine to the besieged Bosnian cities of Maglaj and Tesanj were turned back by armed attacks and bureaucratic obstacles imposed by Serbian nationalist rebels.

Several privately arranged deliveries of vital supplies to isolated Bosnians also have been blocked by combatants who are increasingly using food as a weapon.

At least 150,000 people, mostly Muslims, are stranded in the Maglaj region, which is under steady attack by Serbian and Croatian forces.

“No one will be permitted to plan and organize routes and convoys on their own initiative as it pleases them,” the Bosnian Serb news agency SRNA reported in a dispatch explaining why the U.N. relief convoy was held up in Banja Luka for four days.

“Tesanj and Maglaj have not received any aid except for airdrops for more than 100 days,” said Brett Lodge, a spokesman for the U.N. peacekeeping mission in the former Yugoslav federation. He added that not a single military or relief official has been able to enter the region since it was cut off by Serbian and Croatian attackers in July.

Other U.N. sources say that at least one-third of the nightly airdrops of food by U.S., German and French military planes have missed their targets and landed in areas controlled by Serbian and Croatian attackers.

An airlift into the Serb-encircled Bosnian capital of Sarajevo marked an ominous occasion earlier this week when it surpassed the duration of the 1948-49 Berlin airlift, which lasted 462 days before Communist authorities ceased blocking supplies to the city’s Western sectors.