U.N. Secretary-General Ban Ki-moon is calling on world leaders to unite in a push to speed up the arrival of critical aid supplies in Burma. Mr. Ban says the Burmese government has still not done enough to let in foreign aid. The government has confirmed more than 38,000 deaths in the wake of the cyclone, with more than 27,000 people still missing. But U.N. officials fear the numbers could be far worse - projecting a possible death toll of more than 100,000. From U.N. Headquarters in New York, VOA's Alex Villarreal has more.

Photo released by German aid organization Johanniter shows volunteers as they unpack medical aid for victims of the cyclone in Burma, 13 May 2008

Mr. Ban told reporters Wednesday he is convening key donor countries for a discussion of what he called "concrete measures" to address the cyclone disaster in Burma. He said the meeting will include representatives of the Association of Southeast Asian Nations, which includes Burma.

The secretary-general said he has still not spoken to Burma's leader, General Than Shwe, despite repeated calls and letters. He reiterated his frustration with the military government's response to the crisis.

"Even though the Myanmese government has shown some sense of flexibility, at this time it's far, far too short. The magnitude of this situation requires much more mobilization of resources and aid workers," he said.

Earlier Wednesday, British Prime Minister Gordon Brown proposed that the U.N. hold an emergency summit on Burma and that the secretary-general visit the country.

The U.N. is now seeking $200 million to provide aid to cyclone survivors -- up from last week's appeal for $187 million. U.N. Humanitarian Chief John Holmes said donor nations have already sent or pledged $150 million.

Food, water, sanitation equipment and medical supplies continue to arrive in increasingly large quantities, but Holmes said the biggest problem remains Burma's blocking of the entry of foreign aid workers.

Burma cyclone survivors line up to receive food and water from local donors on the outskirts of Rangoon, Burma, 14 May 2008

"We urge the Myanmar authorities a radical change in this area to allow international staff into the affected area to do the job that they are there to do", he said.

In a move Holmes called a "small sign of selective opening up," the Burmese government invited its immediate neighbors - Thailand, Bangladesh, India and China - to send in 160 humanitarian workers.

Holmes said such progress is still inadequate to meet the needs of the estimated 1.6 million to 2.5 million Burmese severely affected by Cyclone Nargis.