Gordon Brown has demanded that UN special envoy Ibrahim Gambari be allowed to meet democracy campaigner Aung San Suu Kyi when he arrives in Burma.
Aung San Suu Kyi has been under house arrest for several years,
The Prime Minister said that there should also be a formal meeting of the UN Security Council after his visit.
The streets of Rangoon and Mandalay are quiet, with people staying indoors, frightened by the military junta's violent reaction to peaceful protests earlier this week.
Buddhist monks, who had led earlier demonstrations, remain behind the locked doors of monasteries where they have been surrounded by troops.
Mr Brown also called on the international community to step up pressure on Burma and said new EU sanctions must be applied as soon as possible. "The eyes of the world are not only upon (the military junta) but the anger of the world is now being expressed," he said.
"We will now step up our efforts in the international community... to make sure that the democratic aspirations of the Burmese people for reconciliation in their country is impressed on the minds of everybody in the world."
Mr Brown admitted he fears the number of deaths arising from the Burmese military's crackdown on pro-democracy protesters was "far greater" than has been reported so far.
"I am afraid we believe the loss of life is far greater than is being reported so far," he said following talks with US President George Bush and the Chinese Prime Minister Wen Jiabao.
Burmese state television put the death toll from two days of violence at 10, but dissident groups estimate that at least 200 have died.
