May 6 (Bloomberg) -- The death toll from the tropical cyclone that slammed into Myanmar is at least 10,000 and will probably rise, the junta said, making the storm Southeast Asia's deadliest natural disaster since the 2004 tsunami.

About 3,000 people are missing in the Irrawaddy delta region, Myanmar government ministers told international diplomats yesterday, the United Nations news agency IRIN said. Power was knocked out in the former capital, Yangon, and drinking water was contaminated in the city of 5 million people.

``At least eight townships are completely or mostly destroyed,'' said Pamela Sitko, a Bangkok-based worker with the Christian relief group World Vision, who has spoken with colleagues in Myanmar. State media in the country formerly known as Burma reported that ``anywhere from 10,000 to 20,000 people are now dead,'' she said.

In the town of Bogalay alone ``we are getting reports that there are 10,000 dead,'' said Debbie Stothard, a spokeswoman for the civic group Alternative Asean Network on Burma.

The U.S. yesterday offered an initial $250,000 in aid to the country, which is among the world's least-developed, while castigating its military leadership for failing to alert citizens to the approaching cyclone.

``Although they were aware of the threat, Burma's state-run media failed to issue a timely warning to citizens in the storm's path,'' First Lady Laura Bush said from the White House.

New Constitution

Myanmar, a nation of 47.8 million people, is regularly hit by cyclones that form in the Bay of Bengal between April and November. Tropical Cyclone Nargis struck as Myanmar, which has been ruled by the military since 1962, prepares to hold a referendum on May 10 for a new constitution before elections scheduled for 2010.

The junta vowed to press ahead with the referendum after the storm, Agence France-Presse reported, citing a state-run newspaper. The U.S. State Department says the referendum is an attempt by the military to retain power.

Stothard condemned the decision to hold the referendum. ``More and more people are going to die and the regime might not have much of a Burma to rule after this,'' she said from Bangkok.

2004 Tsunami

The disaster is the worst in the region since a 9.1 magnitude earthquake offshore from Aceh on Indonesia's Sumatra island in December 2004 caused a tsunami that swept across the Indian Ocean, devastating coastal communities and leaving more than 220,000 people dead or missing.

``The UN will do whatever it can to provide urgent humanitarian assistance,'' Secretary-General Ban Ki-moon told reporters in New York. ``Because of the lack of communications, we are not quite sure what will be the total extent of damages and casualties. I am very much alarmed by incoming views that casualties have risen to more than 10,000, according to Myanmar's Foreign Ministry.''

Nargis packed winds of 120 miles (190 kilometers) per hour when it struck the coast, sending the sea surging as much 12 feet (3.5 meters).

The government declared a state of emergency in five low- lying provinces, mostly in the rice-growing Irrawaddy delta, where villages were flattened by winds and rain, the UN said.

Myanmar may have to import rice because of ``huge'' damage to crops, said Chookiat Ophaswongse, the head of the Thai Rice Exporters Association.

Rice Exports

The country would probably have exported about 400,000 metric tons of rice this year because of soaring global prices, up from normal shipments of about 100,000 tons, he said in an interview on Bloomberg Television. The storm will definitely ``jeopardize'' exports and it's possible Myanmar will have to import some rice, he said.

State radio warned people to drink boiled water and be wary of mosquitoes and snakes, AFP said.

Houses in Yangon use electricity to pump water, and with power supplies cut by the storm there will be a ``huge water shortage,'' Jyri Rantanen, acting head of disaster management in the Asia Pacific for the International Committee of the Red Cross, said by telephone from Kuala Lumpur.

A UN disaster-assessment team was dispatched to Bangkok, and the world body is prepared to provide a grant from the $500 million Central Emergency Response Fund, created to rush aid to nations in need, spokesman Farhan Haq said.

Stockpiled Food

The UN Children's Fund and its Development Program, which have offices in Myanmar, stockpiled food, water and medicine before the storm. They will distribute water-purification tablets, plastic sheeting, food and cooking sets in Yangon and the delta region.

Flooding, blocked roads and disrupted communications are hampering efforts to assess the extent of the damage, according to the world body.

The junta has requested international assistance and UN officials are engaged in talks with Myanmar authorities on how best to help, IRIN cited Richard Horsey of the UN Office for the Coordination of Humanitarian Affairs as saying.

``Discussions are taking place in New York and on the ground about what is needed,'' he said.

To contact the reporters on this story: Demian McLean in Washington at dmclean8@bloomberg.net; Ed Johnson in Sydney at ejohnson28@bloomberg.net.

Last Updated: May 6, 2008 01:32 EDT