Three weeks after the cyclone's 120 mph (190 kph) winds and sea surge devastated the delta, the U.N. says fewer than one in three of those most in need have received any aid.
Thousands of beggars line the roads, with droves of children shouting "Just throw something" at passing vehicles.
Witnesses say many villages have received no outside help, and waterways of the former Burma's "rice bowl" remain littered with animal carcasses and corpses, either grotesquely bloated or rotting to the bone.
Much of the blame for the aid delay rests with the junta, which has been reluctant to admit a large-scale international relief effort for fear of loosening the vice-like grip on power the army has held since a 1962 coup.
However, top diplomats who helped coordinate a donor conference in Yangon on Sunday said there were small signs of the generals gradually overcoming their pride and paranoia and admitting outside help.
"I can sense that there is a sense of urgency," Surin Pitsuwan, Secretary-General of the Association of Southeast Asian Nations (ASEAN), said in the Thai capital on Tuesday.
"A sense of appreciation that the world, after all, is not all that hostile on some issues, particularly on humanitarian issues," Surin told a news conference.
Washington told the Yangon conference it was ready to raise its offer of $20.5 million in aid if the junta opened up, but added it was "dismayed" the generals went ahead with a constitutional referendum in the middle of the disaster.
The result - 92.5 percent in favour on a turnout of 98.1 percent in a poll held with no neutral monitoring - is unlikely to enhance the credibility of the generals' seven-step "roadmap to democracy", that is meant to culminate in elections in 2010.
After a promise to visiting U.N. chief Ban Ki-moon by junta supremo Than Shwe that all aid workers would be given full access to the delta, foreign experts have headed out of Yangon to test whether anything has changed on the ground.
Myanmar embassies are also granting more visas to aid workers, although the U.N.'s World Food Programme, which is spearheading much of the emergency relief push, says it is coming up against reams of red tape at every turn.
"Yesterday was a record, red-letter day with seven visas applied for and seven issued," WFP spokesman Paul Risley said.
"But every step of the way has been difficult. Every step has required agreement with the government, clearance from the government, approval by the government of virtually all of our actions."
Thomas Gurtner, director of programmes at the international federation of the Red Cross, told Reuters Myanmar had asked the agency to submit a list of priority expatriates and it hoped to deploy an initial batch of six water and sanitation experts into the disaster area in the next few days.
