Yangon, Myanmar ? Myanmar’s monumental task of feeding and sheltering 1.5 million cyclone survivors suffered yet another blow Sunday when a boat laden with relief supplies – one of the first international shipments – sank on its way to the disaster zone.

The death toll jumped to more than 28,000 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.”

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.

But in what was seen as a huge concession by the junta, the United States finally got the go-ahead to send a C-130 cargo plane packed with supplies to Yangon today, with two more air shipments scheduled to land Tuesday.

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.