Yangon, Myanmar - International aid began to trickle into Myanmar on Tuesday, but the stricken Irrawaddy delta, the nation's rice bowl where 22,000 people perished and twice as many are missing, remained cut off from the world.

In the former capital of Yangon, soldiers from the repressive military regime were out on the streets in large numbers for the first time since Cyclone Nargis hit over the weekend, helping to clear away rubble. Buddhist monks and Catholic nuns wielded axes and long knives to remove ancient, fallen trees that were once the city's pride.

However, coastal areas of the delta worst hit by the high winds and tidal surges were out of reach for aid workers, isolated by flooding and road damage.

Electricity remained cut for nearly all 6.5 million residents of Yangon, while water supply was restored in only a few areas. Some residents waited in lines for nine hours or more to buy gasoline to fuel generators and their cars. At one gas station in the Yangon suburb of Sanchaung, fistfights broke out, with weary residents hitting each other with sticks after someone tried to cut in line.

The U.N.'s World Food Program said international aid began to flow, with 800 tons of food getting through to the first of nearly 1 million people left homeless by the cyclone.

Concerns mounted over the lack of food, water and shelter in the delta region and adjacent Yangon, where nearly a quarter of Myanmar's 57 million people live, as well as the spread of disease in a country with one of the world's worst health systems.

"Our biggest fear is that the aftermath could be more lethal than the storm itself," said Caryl Stern, who heads the U.N. Children's Fund in the United States.

After days of little military presence in the streets, soldiers were out Tuesday clearing massive felled trees with power saws and axes and using their bare hands to lift debris into trucks.

State television played up the effort, showing images of a government truck distributing water, though residents said they hadn't seen any water trucks around the city. There were no images of the hundreds of monks helping the recovery effort.

The streets of Yangon were filled Tuesday with residents carrying buckets to bring water from monasteries or buy it from households with generators that could pump it from wells. The main plant of Dagon Ice Factory, a drinking water brand, turned people away, posting signs saying "no more."

While residents of Yangon struggled to clear away the rubble, the Irrawaddy delta was cut off.

Images on state television Tuesday showed mangled trees and electricity poles sprawled across roads as well as roofless houses ringed by water in the delta, a lacework of paddy fields and canals where the nation's rice crop is grown.

Based on a satellite map made available by the United Nations, the storm's damage was concentrated over about a 11,600-square-mile area along the Andaman Sea and Gulf of Martaban coastlines - less than 5 percent of the country, but home to nearly a quarter of the country's population.

A C-130 military transport plane carrying government aid from neighboring Thailand flew into Yangon, where an Associated Press reporter watched it unload rice, canned fish, water and dried noodles. The goods_ the first overseas aid to arrive in the stricken nation - were transferred to a helicopter, which Myanmar military officers said would ferry them to the most stricken areas.

The White House said Tuesday the U.S. would send more than $3 million to help cyclone victims, following an initial emergency contribution of $250,000.

President Bush called on the junta to allow the United States to send in a disaster assessment team, which he said would allow for quicker and larger aid infusions.

"The United States has made an initial aid contribution but we want to do a lot more," Bush said. "We're prepared to move U.S. Navy assets to help find those who have lost their lives, to help find the missing, to help stabilize the situation. But in order to do so, the military junta must allow our disaster assessment teams into the country."

Bryan Whitman, a Pentagon spokesman, said the Navy has three ships in the Gulf of Thailand - the USS Essex, the USS Juneau and the USS Harper's Ferry - preparing to participate in an annual exercise with Thailand's naval forces.

Pentagon press secretary Geoff Morrell said two aircraft carriers - the USS Kitty Hawk and the USS Nimitz - as well as the USS Blue Ridge, are also within reach of Myanmar. The Essex, an amphibious assault ship, has 23 helicopters aboard, including 19 that are capable of lifting cargo from ship to shore, as well as 1,800 Marines.

The Myanmar military, which regularly accuses the United States of trying to subvert the regime, is unlikely to allow a U.S. military presence in its territory.

But reflecting the seriousness of the crisis, the government has appealed for foreign aid and also announced Tuesday that it is delaying a crucial constitutional referendum in the hardest-hit areas.

State radio said Saturday's vote on a military-backed draft constitution would be delayed until May 24 in 40 of 45 townships in the Yangon area and seven in the wider delta.

Pro-democracy advocates, including the political party of detained Nobel laureate Aung San Suu Kyi, have denounced the constitution as a tool to perpetuate the military's grip on power.

Inadequate warnings about the approaching storm and the ineffectiveness of the government in its aftermath could sway angry voters to reject the charter.

State radio said most of the 22,464 dead, as well as the 41,000 missing, were in the densely populated Irriwaddy delta, home to 6 million people. It said 671 were killed in the Yangon area. Brig. Gen. Kyaw San, the information minister, said most fatalities were caused by tidal waves.

The death toll is the highest from a natural disaster in southeast Asia since the tsunami of December 2004 killed 229,866 people in Indonesia, Thailand and other parts of southeast and south Asia.

With 61 dead, Myanmar was largely spared the devastating impact of the tsunami, which killed 130,000 people in Indonesia and 35,000 in Sri Lanka. In its wake, an extensive warning system was established in much of the Pacific region, but Myanmar did not participate. Disaster experts cited lack of funding and said the country planned to rely on regional systems.

As the cyclone came bearing down on Myanmar late Friday, television broadcasts warned of 120-mph winds and 12-foot storm surges. But electricity is so spotty in Myanmar that few households, especially in the poor rural areas that were worst hit, were aware of the warnings.

The U.N. World Food Program offered a grim assessment of the destruction: up to 1 million people homeless, some villages almost totally destroyed and vast rice-growing areas wiped out.

Rice futures rose Tuesday in response to the news that vast swaths of Myanmar's rice-growing areas had been wiped out. Myanmar grows 11 million tons of rice per year but exports only a small fraction, representing about 1.7 percent of world trade, according to USDA figures.

It had been forecast to export about 400,000 tons this year, and concerns that Myanmar may not meet that target helped push U.S. rice futures 10 cents higher to settle at $21.15 per 100 pounds Tuesday on the Chicago Board of Trade.

The military government said it was trying to move in aid and some foreign agencies managed to send assessment teams, including five from UNICEF.

Richard Horsey, Bangkok-based spokesman for the U.N. Office for the Coordination of Humanitarian Aid, noted the closest airport to the Irriwaddy delta is in Yangon.

"The biggest problem will be to reach the affected areas. There will be a huge logistical problem," he said, adding that "for remote areas, assessment teams ... will need to go by helicopters and boats."

The delta is criss-crossed with waterways, but Horsey said they are not easily accessible, even during normal times.

"The big concern is waterborne diseases. So that's why it's crucial to get safe water in. Then mosquito nets, cooking kits and clothing in the next few days," he said. "Food is not an emergency priority. Water and shelter are."