* U.N. says 1.5 million people "severely affected"
* U.S. outraged by Myanmar government's slow response
* U.N. chief says wants talks with Myanmar top general
* U.S. Navy sends ships with aid toward Myanmar (Adds Indonesian, British response to French U.N. proposal)
By Louis Charbonneau
UNITED NATIONS, May 8 (Reuters) - The United Nations estimated 1.5 million people have been "severely affected" by the cyclone that swept through Myanmar, with the United States expressing outrage on Thursday at delays in allowing in aid.
In Myanmar, desperate survivors cried out for food, water and other supplies nearly a week after 100,000 people were feared killed by Cyclone Nargis as it roared across the farms and villages of the low-lying Irrawaddy delta region.
"We're outraged by the slowness of the response of the government of Burma (Myanmar) to welcome and accept assistance," U.S. 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 U.N. 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.
U.S. 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.
U.N. 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 U.N. 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.
U.N. 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 leveled 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 U.N. 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 U.N. 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.
Shari Villarosa, charge d'affaires of the U.S. embassy in Myanmar, said on Wednesday the death toll may exceed 100,000.
About 1 million people were left homeless.
U.N. officials who had earlier complained the generals were putting up obstacles to an emergency airlift, said half a dozen cargo planes had been allowed to land at Yangon airport.
The Red Cross/Red Crescent confirmed its first aid plane took off from Kuala Lumpur, carrying six tonnes of shelter materials. The World Food Program said it delivered 7 metric tons of high-energy biscuits to Yangon and two more aid flights were en route with clearance to land.
World Food Program spokesman Paul Risley said aid agencies normally expect to fly in experts and supplies within 48 hours of a disaster but, nearly a week after this cyclone, few have been able to send reinforcements into Myanmar.
'RESPONSIBILITY TO PROTECT'
France has suggested invoking a U.N. "responsibility to protect" to deliver aid to Myanmar without government approval. But its bid to make the Security Council take a stand has been rebuffed by China, Vietnam, South Africa and Russia.
The U.N. envoys of Indonesia and China spoke against politicizing the issue.
"There is already a readiness on the part of Myanmar to open itself to assistance," Indonesian Ambassador Marty Natalegawa told reporters. "The last thing we would want is to give a political spin to the technical realities and the situation on the ground."
Sawers, the British envoy, suggested that Britain also had doubts about invoking the "responsibility to protect" idea.
"That (concept) relates to acts of genocide, war crimes, crimes against humanity and so forth, rather than responses to natural disasters," Sawers told reporters.
German Foreign Minister Frank-Walter Steinmeier called his Myanmar counterpart, Nyan Win, on Thursday and urged him to make it possible for international aid workers and relief organizations to reach hard-hit areas.
The relief agency Medicins sans Frontieres, which has 1,238 people in Myanmar, said it was ferrying aid into the delta via trucks and boats.
"The roads are very poor or destroyed, and in many cases there were no roads before," said Jean-Michel Grand, executive director of Action Contre la Faim in London. "Everybody's looking at boats."
Thai Prime Minister Samak Sundaravej failed to reach Myanmar's generals on Thursday due to communications problems after U.S. President George W. Bush asked him to intervene over the aid delays, Thailand's government spokesman said.
"Some (aid) is getting through," World Vision Australia's chief executive officer Tim Costello told reporters in a conference call from Yangon. "But it's a trickle when it needs to be literally a flood." (Additional reporting by Aung Hla tun in Yangon, Nopporn Wong-Anan, Grant McCool and Darren Schuettler in Bangkok, Jalil Hamid in Kuala Lumpur, Kerstin Gehmlich in Berlin, Matthew Bigg in Atlanta and Claudia Parsons at the United Nations; Writing by Bill Tarrant; Editing by John O'Callaghan)