Large quantities of international aid are being delivered to the region but are awaiting permission for delivery to areas hardest-hit by the cyclone.
According to the Red Cross, aid agencies have been able to reach only around 20% to 30% of cyclone victims and hundreds of thousands of people are at risk of diseases such as dysentery because of lack of clean water.
"If clean water isn't available, it's going to be the biggest killer in the post-disaster environment," Thomas Gurtner told The Associated Press.
"Food is urgent but you die in three days from acute diarrhoea. You die of starvation in a period of weeks.
"The immediate life-savers are water and shelter."
The Association of South East Asian Nations is due to hold a high-level meeting in the coming days that is expected to lay the framework for a broader aid donors conference.
Burma's military leadership has warned that those who hoard or sell aid on the black market will be prosecuted, amid international reports of misuse of some aid shipments.
The generals have also lauded what they said was a 92% approval of a new constitution in a referendum held last Saturday.
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