It said "the number of deaths could range from 63,290 to 101,682, and 220,000 people are reported to be missing". It said "acute environmental issues" posed a threat to life and health.
"Unless there is a massive and fast infusion of aid, experts and supplies into the hardest-hit areas, there's going to be a tragedy on an unimaginable scale," said Greg Beck of the International Rescue Committee.
In the delta town of Labutta, where 80 percent of homes were destroyed, authorities were providing one cup of rice per family per day, a European Commission aid official told Reuters.
In a blow to the stumbling relief effort, a boat carrying some of the first aid to survivors sank, the International Federation of Red Cross and Red Crescent Societies said.
The boat was believed to have hit a submerged tree in the Irrawaddy delta. The accident highlighted the enormous logistical difficulties of delivering aid, with roads washed away and much of the delta turned to swamp.
Burma raised the death toll on Sunday to 28,458 dead and 33,416 missing from the storm on the night of May 2 and early on May 3. Most of the victims were killed by the 12-foot (3.5 metre) wall of sea-water that hit the delta along with the Category 4 cyclone's 190 kph (120 mph) winds.
U.N. LEADS AID EFFORT
Australia responded to a U.N. appeal for $187 million in aid by dramatically increasing its contribution to $23.4 million.
The U.N. World Food Programme said on Sunday it has begun moving aid to its field headquarters in Labutta using trucks provided by the Myanmar Red Cross and other local partners.
"I think you can say it continues to trickle in," WFP spokesman Marcus Prior said on Monday.
The more than one million worst affected lack food, water, and sanitation, face outbreaks of disease such as cholera, and heavy rains are predicted this week over the delta.
Three U.S. Navy ships are steaming toward Burma, and a French warship was expected near Burma's waters later this week, carrying 1,500 tonnes of rice that France said it wants to distribute directly to survivors.
Despite the alarm bells from the international community about the feeble cyclone relief effort, the junta kept its focus on a weekend referendum on a new constitution, part of a "roadmap to democracy" culminating in multi-party elections in 2010.
There is little doubt about the final result on an army-drafted constitution after an intensive propaganda campaign by the junta urging people to vote "Yes".
