YANGON, Myanmar — The United Nations has received permission from Myanmar to use nine helicopters to ferry relief supplies to stranded cyclone victims, U.N. Secretary-General Ban Ki-moon said Tuesday as he warned that relief efforts are at a "critical moment."

"We have received government permission to operate nine WFP (World Food Program) helicopters, which will allow us to reach areas that have so far been largely inaccessible," Ban told reporters in New York before departing on a trip to Myanmar.

His announcement was not immediately confirmed by officials of Myanmar's military government.

"I believe further similar moves will follow, including expediting the visas of (foreign) relief workers seeking to enter the country," Ban said. "I'm confident that emergency relief efforts can be scaled up quickly."

U.N. Undersecretary-General for Humanitarian Affairs John Holmes was in Myanmar seeking to persuade the junta to let in more international assistance and paving the way for Ban's visit, which begins Thursday.

Holmes said he told Myanmar's prime minister, Lt. Gen. Thein Sein, that the U.N. wants to support aid efforts, "as we would do in any other country in any disaster of this scale, where clearly the size of the tragedy outweighs the capacity of any country to deal with it by itself."

The junta appears to be slowly relenting to foreign pressure to accept more outside help, but even foreign aid workers already in the country are still banned from the worst devastated areas. The U.N. said only a fraction of survivors had gotten any international assistance.

The official death toll stood at about 78,000, with 56,000 more people missing. Conditions in the low-lying Irrawaddy River delta remained precarious, with survivors facing disease, malnutrition and exposure to the elements.

Speaking at a news conference a day after visiting the delta, Holmes said he had suggested the junta make "better use of international expertise and assets" and ensure "all possible routes in for aid are open, whether they be by land or sea or air."

The U.S. military has several helicopters on standby on a warship off the Myanmar coast and in neighboring Thailand.

The U.S. is already flying supplies in from Thailand on C-130 cargo aircraft, at a rate of about five flights a day. But the planes go to Myanmar's biggest city, Yangon, from which it is a difficult journey to the Irrawaddy delta.

Ban is expected to visit areas devastated by Cyclone Nargis as well as talk with officials and aid workers. On Sunday, he is scheduled to attend a meeting of aid donors in Yangon. Myanmar, one of the world's poorest nations, claims losses from the disaster exceeded $10 billion.

At U.N. headquarters, Ban said he was confident aid efforts can be increased and welcomed the junta's "recent flexibility" in allowing relief workers from the 10-member Association of Southeast Asian Nations to begin distributing aid.

Myanmar's leaders began three days of mourning for the dead and missing. Flags at government offices, schools and large hotels flew at half staff, but shops opened and many people in Yangon said they had little idea what the official mourning entailed.

Others were angry.

"I don't think flying flags at half-mast is going to help. If they are sincere, they should welcome help from everyone," said Zin Moe, a 32-year-old clothes vendor. "They are not letting in aid quickly enough and people are angry."

State-owned media quoted Senior Gen. Than Shwe, the junta leader, as saying the government has spent $45.5 million on relief operations, has met immediate needs such as food, shelter and health care and is moving into the reconstruction phase.

Foreign aid agencies and U.N. officials were less upbeat.

"I think there is still a long way to go to improve the relief efforts, to speed it up and to make sure that all the people who are in need are reached," said Holmes. "There is still a major effort to be mounted on the relief side which has to go on for some three to six months."

Holmes said his tour of the delta found the worst damage in the southernmost areas closest to the coast.

"Everything in the path of the tidal surge has been almost completely destroyed, including villages," he said. "There was nothing left of the houses, and you can imagine what had happened to the people inside these houses, which is no doubt why the death toll has been so high."

A Myanmar doctor returning to Yangon from the delta said refugees in the bigger towns were getting some aid and medical care, but she expressed concern for those in outlying villages. Villagers were still trickling into towns because they had gotten no aid, Tin Sein said.

"We saw one young girl yesterday. Her lips and her nails were blue. She looked like she was going to die," Tin Sein said. "People haven't eaten or drunk clean water and are completely exposed to the rains and storm."