"We're outraged by the slowness of the response of the government of Burma (Myanmar) to welcome and accept assistance," US Ambassador to the United Nations, Zalmay Khalilzad, told reporters.

"It's clear that the government's ability to deal with the situation, which is catastrophic, is limited."

The UN food agency and Red Cross/Red Crescent said they had finally started flying in emergency relief supplies after foot-dragging by Myanmar's ruling military junta. The United States was waiting for approval to start military flights.

US Defense Secretary Robert Gates told reporters that Washington was "fully prepared to help and to help right away, and it would be a tragedy if these assets" were not used.

The Navy said four ships, including the destroyer USS Mustin and the three-vessel Essex Expeditionary Strike Force, were heading for Myanmar from the Gulf of Thailand after the Essex deployed helicopters to Thailand for aid operations.

Witnesses have seen little evidence of a relief effort in the delta that was swamped in Saturday's storm. It was the worst cyclone in Asia since 1991, when 143,000 people were killed in neighboring Bangladesh.

"We'll starve to death if nothing is sent to us," said Zaw Win, a 32-year-old fisherman who waded through floating corpses to find a boat for the two-hour journey to Bogalay, a town where the government said 10,000 people were killed.

REMOVING OBSTACLES

UN Secretary-General Ban Ki-moon said he was seeking direct talks with the junta's senior general, Than Shwe, to persuade him to remove obstacles. A UN spokeswoman said Ban believed it might be "prudent" for the government to postpone a constitutional referendum planned for Saturday.

Some critics accuse the junta of stalling because they do not want an influx of foreigners into the countryside during the referendum on the army-drafted constitution that looks set to cement the military's grip on power.

UN humanitarian affairs chief John Holmes was asked by reporters if he suspected a link between the referendum and Myanmar's reluctance to grant visas to aid workers.

"The referendum may or may not be a complicating factor but as I say my focus is really on getting the aid to people as fast as possible," Holmes said.

Ban said in an interview on CNN it was "already very late" for taking immediate post-cyclone action but not too late for Myanmar's junta to accept help.

"Now, before it is too late, I would again urge and appeal to Myanmar authorities to be flexible in dealing with these humanitarian issues with a strong sense of urgency," Ban said.

Washington was hoping to get approval to send in a plane with aid that is ready to fly. Approval for such a flight would be significant, given the huge distrust and acrimony between the former Burma's generals and Washington, which has imposed tough sanctions to try to end 46 years of military rule.

AID PLANES ARRIVE

The storm pulverized the Irrawaddy delta with 120 mph (190 kph) winds followed by a 12-foot (3.7-metre) wave that levelled villages and caused most of the casualties and damage.

While Holmes said the United Nations estimated at least 1.5 million people were "severely affected," Britain's UN Ambassador John Sawers said it may be in the millions.

Holmes also told reporters he was "disappointed" with the lack of progress being made in getting UN aid in.

Myanmar state television did not give an update on Thursday night of the death toll, which stood at 22,980 with 42,119 missing as of Tuesday. Diplomats and disaster experts said the real figure is likely to be much higher.