The international community must step up its efforts to end the "humanitarian disaster" in Burma, Gordon Brown has said.
Over 133,000 people are now believed to be dead and missing in the aftermath of Cyclone Nargis, which hit the south-east Asian country earlier this month.
The military junta which rules Burma has come under criticism for its reluctance to allow aid into the country, prompting condemnation from the rest of the world.
In an interview with the BBC, Mr Brown said the UK government was "determined" to make the $35 million of aid it is offering available to those who need it most.
"I think it is unfortunate that the regime has made it very difficult to get the aid to people," he said.
"This is a natural disaster which has become a manmade disaster by the failure of the regime to use what aid is available… and I urge all those who are part of the government to do everything in their power to get the aid to those people who need it most."
Some, including a group of US lawmakers lobbying president George Bush, have called for the principle of "humanitarian intervention" to be invoked.
This could involve airdrops of aid over the affected areas without permission from Yangon. Mr Brown is ruling this out – for now.
"There is a question of airdrops, invoking or supporting the responsibility to protect, but the quickest, most effective and most rapid way of getting aid to the people of Burma is that the government will cooperate and make it possible for the aid to be distributed," he added.
Britain is seeking an additional meeting on the issue at the United Nations in New York. The UN's secretary-general Ban Ki-moon is in the region while India, China, the EU and the Association of South-east Asian Nations (Asean) are also working on the issue, Mr Brown added.
"Concerted pressure that we are beginning to bear… is the lever that we've got to continue to force out there," he said.
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