The international community has flown in tonnes of medicine, food and shelter materials, but getting it to low-lying delta area has been complicated by poor equipment, bad weather and government intransigence.
Heavy rains have pelted the low-lying delta region, slowing the transportation of aid by land and adding to the misery of tens of thousands of refugees sandwiched into monasteries, schools and pagodas.
The international community has warned of an even greater tragedy if the aid effort is not ratcheted up.
Lacking food, water and sanitation, survivors of Cyclone Nargis face the threat of killer diseases such as cholera and in some areas are waiting in vain for help to arrive.
"If these people aren't reached and aid got to them quickly, and shelter and toilet facilities, disease will break out," the International Rescue Committee's Bacon said.
The WFP said it was looking for helicopters to airlift rice and high-energy biscuits down to the delta and also boats to reach isolated communities along the Irrawaddy river.
It said it had provided food to 50,000 people and aimed to reach 750,000 over the next six months.
Operations in Myanmar are a shadow of the massive international relief operation kick-started just days after the 2004 Asian tsunami.
The United States alone deployed thousands of its military and more than a dozen ships in the Indian Ocean, and many other countries provided major help.
But Myanmar's junta has made it clear it does not want Westerners distributing aid.
Foreign experts in sanitation, nutrition and medicine have either been prevented from entering the country formerly known as Burma or are restricted to Yangon.
Armed police send back foreigners who attempt to pass through checkpoints surrounding the former capital.
In a statement after emergency talks on Myanmar in Brussels on Tuesday, EU development ministers called on Yangon "to offer free and unfettered access to international humanitarian experts, including the expeditious delivery of visa and travel permits."
The EU ministers stopped short of endorsing a French call to deliver supplies if necessary without the junta's permission.
