The regime said the national mourning period would begin with the lowering of all flags to half mast on Tuesday -- 18 days after Cyclone Nargis first pummelled this isolated and impoverished country once known as Burma.

The reclusive junta leader Than Shwe spent a second consecutive day Monday touring the disaster zone, venturing into the hardest-hit regions of the Irrawaddy Delta for the first time, state television said.

Until Sunday, the senior general had not made a single public appearance or remark about the disaster that has left at least 133,000 dead or missing.

Despite the gentler tone, Myanmar stopped short of allowing a full-scale relief operation, even in the face of warnings that people could soon start to die without help.

Myanmar did agree at regional talks in Singapore to allow the Association of Southeast Asian Nations (ASEAN) to coordinate an international relief effort, after resisting multiple foreign attempts to deliver aid to hard-hit areas.

The U.N.'s top aid official John Holmes was finally allowed Monday to glimpse just how desperate the situation has become, as he toured part of the southern delta, where entire villages were washed away.

Despite Myanmar's compromise with ASEAN, the regime has yet to soften its refusal to allow in foreign aid workers in the numbers needed to reach the estimated 2.4 million people still in desperate need.

Singapore Foreign Minister George Yeo said after hosting his counterparts in the city-state that Myanmar's Nyan Win had put the damage from the cyclone at more than US$10 billion.

Yeo said the junta also had agreed to accept the immediate despatch of medical teams from other ASEAN nations.