Nearly 32,000 people were killed by the cyclone on May 3 and almost 30,000 others are still missing, according to Burma state television.

"We believe that it's going to be very difficult to reach everybody and to tackle the crisis as we would like without some outside military and civilian assets," John Holmes, the UN's top humanitarian official, told reporters.

Almost all foreign relief workers have been barred entry into the isolated nation. The junta says it wants to hand out all donated supplies on its own.

"I want to register my deep concern -- and immense frustration -- at the unacceptably slow response to this grave humanitarian crisis," Ban said.

"Unless more aid gets into the country -- very quickly -- we face an outbreak of infectious diseases that could dwarf today's crisis. I therefore call, in the most strenuous terms, on the government of Burma to put its people's lives first. It must do all that it can to prevent this disaster from becoming even more serious."

Ban said Burma's leaders had not returned his repeated calls and letters to them, including a second letter sent on Monday, seeking greater cooperation with the UN and other international relief efforts.

Meanwhile three of the UN Security Council's five veto-wielding members -- France, Britain and the US -- remained interested in possible action to require Burma's government to open its doors to more aid, US and other council diplomats said.

"We'll be pushing the issue in the council," deputy US ambassador Alejandro Wolff said.

There is no agreement on proposed wording for a statement or resolution, but US officials say their aim is to craft language saying authorities in Burma must do everything possible to accept international help.