YANGON, Myanmar - The grim forecast came as heavy rains drenched the devastated Irrawaddy River delta, disrupting aid operations already struggling to reach up to 2.5 million people in urgent need of food, water and shelter.

"Another couple of days exposed to those conditions can only lead to worsening health conditions and compound the stress people are living in," said Shantha Bloemen, a spokeswoman for UNICEF.

A tropical depression in the Bay of Bengal added new worries, but late in the day forecasters said it was weakening and unlikely to grow into a cyclone.

Myanmar's government issued a revised casualty toll Wednesday night, saying 38,491 were known dead and 27,838 were missing.

The International Federation of Red Cross and Red Crescent Societies, however, said its estimate put the number of dead between 68,833 and 127,990. The Geneva-based body said the range came from a compilation based on other estimates from 22 different organizations, including the Myanmar Red Cross Society, and on media reports.

Even though the figures seemed precise, spokesman Matthew Cochrane said they were not based on body counts, but were only rough estimates designed to provide Red Cross donors and partner organizations with an idea of the numbers being discussed within the aid community.

UN officials have said there could be more than 100,000 dead.

The Red Cross estimated the number of people needing help after cyclone surged over the low-lying delta on May 3 at between 1.64 million and 2.51 million.

But the junta still refused to accept help from foreign aid experts, who have vast experience in handling humanitarian crises.

It insisted Myanmar can handle the disaster on its own - a stance that appeared to stem not from the isolationist regime's ability but from its deep suspicion of most foreigners, who have frequently criticized its human rights abuses and crackdowns on democracy activists.

Meanwhile, UN Secretary General Ban Ki-moon said he secured support from Myanmar to increase the flow of relief aid.

"In view of the magnitude of this crisis, much more needs to be done," Ban told reporters after a nearly two-hour meeting in New York with Myanmar, its neighbours and key donors. The "Myanmese ambassador has assured that the Myanmese government will do all to assist."

Ban also said that during the meeting aimed at boosting aid to the stricken nation he was also able to win backing from the groups for a high-level conference to raise funds for disaster aid this month.

Myanmar's prime minister, Lt.-Gen. Thein Sein, told visiting Thai Prime Minister Samak Sundaravej on Wednesday that the government was in control of the situation and didn't need foreign experts.

"They have their own team to cope with the situation," Samak said after returning to Bangkok. He said the junta gave him a "guarantee" that there was no starvation or disease outbreaks among survivors.

But critics say the government is woefully lacking in helicopters, trucks and boats as well as planning expertise needed to distribute aid to survivors, who have jammed into monasteries and relief centres or are camping outside.

UN agencies and other voluntary groups have been able to reach only 270,000 of the affected people, said Elisabeth Byrs of r the UN Office for Humanitarian Affairs in Geneva.

She said the World Food Program would need 55,000 tonnes of rice to feed 750,000 people for three months, but the agency had been able to ship in only 361 tonnes so far.

On Thursday, aid agencies were preparing or moving in a wide-range of relief supplies including material for temporary shelters, rice, drinking water, kitchen utensils and medicines including 2,000 anti-snake bite kits. The UN World Health Organization says an increase in snake bites is feared in coming days.

The junta did grant approval Wednesday for a Thai medical team to visit the delta, said Dr. Thawat Sutharacha of Thailand's Public Health Ministry. If the team goes as scheduled Friday, it will be the first foreign aid group to work in the ravaged delta.

Myanmar has limited the few international aid workers in the country to Yangon, the country's biggest city, and used police to keep foreigners from going to the delta.

The UN has also expressed concern this week that some of the food and aid donated by international groups isn't making it to the most needy, but is being diverted by officials or the military. And some aid workers and survivors said that in many cases spoiled or poor-quality food was being given to survivors.

Zalmay Khalilzad, the American ambassador to the UN has said the U.S. is concerned about the issue and wants to make sure that that aid goes to the people that are intended to be the recipients.

The government gave a little ground to demands that it let in more experts. It announced it would allow in 160 relief workers from neighbouring countries - India, China, Bangladesh and Thailand. Except for the Thais, it was not clear whether they would be permitted to go to the delta. The UN also said that an emergency rapid assessment team from the Association of Southeast Asian Nations was being assembled for movement into Myanmar within the next 24 hours.

In New York, UN humanitarian chief John Holmes welcomed the junta's move to let in the Asian relief workers. But he said it was not enough and demanded that Myanmar open its borders to foreign relief specialists and let outsiders work in the Irrawaddy delta.

"The relief getting through under the kind of restrictions we're operating under is by no means adequate to the task, and it's hard to see how just continuing with the status quo can ever be sufficient in the current critical time period that we're working in," Holmes said.

While it has kept out all but a few foreign aid workers, the regime has accepted tons of provisions sent by international donors, including the United Nations and the United States.

Five U.S. C-130 military transport planes delivered drinking water, blankets, mosquito nets and plastic sheets Wednesday. Lt.-Col. Douglas Powell said about 90,000 kilograms of provisions had been sent in on eight U.S. flights since Monday.

Adm. Timothy Keating, head of the U.S. Pacific Command, said he did not get the junta's formal approval for American aid flights when he met with the Myanmar navy commander Monday in Yangon. But he said Myanmar officials were allowing the planes to fly in.

"In approving our flight plans, they are giving us permission - it is kind of implicit permission," Keating said in an interview with National Public Radio's "Morning Edition" program.

The State Department renewed an appeal for the junta to allow in outside disaster relief experts and more assistance. "This is not a political issue. This really is simply a humanitarian issue," said deputy spokesman Tom Casey.

The European Union's top aid official, Development Commissioner Louis Michel, said he was not opposed to the idea of parachuting aid into Myanmar, but said he did not think it was workable. Others have suggested unilateral air drops to circumvent the junta's restrictions.