The United States launched its first relief airlift to Myanmar on Monday, after prolonged negotiations with the isolated country's military rulers, who have been accused of restricting international efforts to help as many as 1.5 million cyclone survivors at risk of disease and starvation.

The flight took off from a base in Thailand a day after the monumental task of feeding and sheltering the survivors suffered yet another blow when a boat laden with relief supplies _ one of the first international shipments _ sank on its way to the disaster zone.

The junta has been sharply criticized for its handling of the May 3 disaster, from failing to provide adequate warnings about the pending storm to responding slowly to offers of help.

Though international assistance has started trickling in, the few foreign relief workers who have been allowed entry into Myanmar have been restricted to the largest city of Yangon. Only a handful have succeeded in getting past checkpoints into the worst-affected areas.

The death toll jumped to more than 28,000 on Sunday and British Foreign Secretary David Miliband warned that "malign neglect" by the isolated nation's military rulers was creating a "humanitarian catastrophe of genuinely epic proportions."

But in what was seen as a huge concession by the junta, it gave the United States, which it views as its enemy, the go-ahead to send a C-130 cargo plane packed with supplies to Yangon on Monday. Two more air shipments were scheduled to land Tuesday.

The C-130, loaded with 28,000 pounds of supplies, including mosquito nets, blankets and water, took off from the Thai air force base in Utapao. Lt. Col. Douglas Powell, U.S. Marines spokesman for the operation, said the plane was carrying U.S. government, not military, supplies and was unarmed.

Myanmar's military rulers are deeply suspicious of Washington, which has long been one of the junta's biggest critics, pointing to human rights abuses and its failure to hand over power to a democratically elected government.

"We hope that this is the beginning of a long line of assistance from the United States," White House spokesman Gordon Johndroe told reporters in Crawford, Texas over the weekend. "They're going to need our help for a long time."

Highlighting the many challenges ahead, however, a Red Cross boat carrying rice, drinking water and other goods for more than 1,000 people sank Sunday near hard-hit Bogalay town. All four aid workers on board were safe.

The International Federation of Red Cross and Red Crescent Societies could not say how much of the cargo has been lost, but it said the food supplies were contaminated by river water.

"Apart from the delay in getting aid to people we may now have to re-evaluate how we transport that aid," said Michael Annear, the IFRC's disaster manager in Yangon, who described the sinking as "a big blow."

Other aid was increasingly getting through, the group said, but on "nowhere near the scale required."

Heavy showers were forecast for the coming week, further complicating delivery of aid that is still barely reaching victims in the Irrawaddy delta, which was pounded by 120 mph winds and 12-foot-high storm surges from the sea.

In hard hit Laputta, hundreds of survivors crowded the floor of a monastery's open-air hall, the sound of hungry children wailing. Many people tried to sleep sitting up because of lack of space.

Pain Na Kon, a tiny nearby village of just 300, was completely obliterated. The only 12 known survivors huddled together in a tent set up in a rice field, sharing a small portion of biscuits and watery soup handed out at a local monastery.

"We don't know when they will also run out of food," said U Nyo, casting glances at his 6-year-old niece, Mien Mien, who lost both her parents in the cyclone and sat outside in the dark.

U Nyo called out to her gently, but Mien Mien stared emptily into the darkness. Overcome with emotion, U Nyo walked, teary-eyed, over to the girl and sat beside her in silence.

His wife, Saw San Myant, described in a hushed voice what had happened to Mien Mien's father.

"We hung together on a coconut tree as the tide continued to rise. Her father was separated. He tried to hang onto a pole of the hut but that was broken. The wind was too strong. She saw her father swept away by the water but we didn't see anyone else. We think they are all dead," she said.

On Sunday, Myanmar's state television said the death toll from Cyclone Nargis had gone up by about 5,000 to 28,458 _ with another 33,416 missing _ though some experts said it could be 15 times that if people do not get clean water and sanitation soon. The U.N. said about 2 million people were severely affected by the storm.

"A natural disaster is turning into a humanitarian catastrophe of genuinely epic proportions in significant part because of the malign neglect of the regime," said British Foreign Secretary David Miliband.

"I would be amazed if there hadn't been about 100,000 who had died already ... what's more, hundreds of thousands more are at risk," he told British Broadcasting Corp. television.

Meanwhile, aid was piling up in foreign countries, awaiting approval from the junta.

The country's main airport in Yangon is incapable of handling more than five flights a day, when it should be taking in at least one every hour, said PLAN, a London-based children's aid group.

"Logistically, the situation looks bleak," it said in a statement. "In short, they have one congested airport, ill equipped to deal with the influx of cargo, no port, restricted fuel and no trucks."

Aid group World Vision said it has requested visas for 20 people and received approval for two, while the U.N. World Food Program had one approved out of the 16 it requested. Still, the U.N. was making some progress in aid delivery.

The junta released 38 tons of high-energy biscuits to the WFP that were confiscated on Friday and several other shipments were on their way.

"We're delighted and very encouraged by what is a very positive sign," said the group's spokesman, Marcus Prior.

But World Vision, which has a big presence in Myanmar, said relief material delivered so far is a tiny fraction of what is needed.

The junta says it wants to hand out all donated supplies on its own.

But many survivors have been without help for more than a week after fleeing their inundated villages to take shelter in monasteries and schools in towns. The canals and flooded roads to higher ground were littered with the bloated bodies of humans. The stench was everywhere.

"The first few we saw, we were all very shocked," said U Pinyatale, a monk living near the Pyapon River, where dozens of corpses floated in the brackish waters. "After a while, there were just too many."