UN Secretary General Ban Ki-moon has urged Myanmar's military government to focus on its national tragedy in the wake of Cyclone Nargis as it prepared instead to hold a referendum this weekend on a new constitution.

Ban hinted that the referendum should be postponed, while the United Nations urged the international community to help the more than one million victims of the cyclone, which has killed an estimated 23,000 people with tens of thousands still missing.

'The secretary general, deeply concerned about the welfare of the people of Myanmar at this time of national tragedy, has taken note of the government's decision to proceed with the constitutional referendum on May 10,' a UN statement said.

The Myanmar government has decided to postpone the referendum only in those areas worst hit by the storm.

'Due to the scope of the disaster facing Myanmar today, however, the secretary general believes that it may be prudent to focus instead on mobilizing all available resources and capacity for the emergency response efforts,' the statement said.