UN Secretary General Ban Ki-moon left for Myanmar Tuesday, calling the situation there "critical" with relief efforts reaching only a quarter of those in need.
Ban also said that Myanmar had granted permission for nine World Food Program helicopters to operate in remote areas.
"This is a critical moment for Myanmar. We have a functioning relief program in place but so far we have been able to reach only about 25 percent of Myanmar's people in need," Ban told reporters at UN headquarters.
Ban, set to arrive in Myanmar early Thursday after a stop in Thailand, planned to visit the worst-hit Irrawaddy delta region and to attend weekend fund-raising talks in Yangon.
The UN chief has warned of a second catastrophe -- the potential for disease to prey on weakened survivors -- and will appear in person to try to persuade Myanmar's military junta to accept more international aid for some 2.4 million survivors.
He said his aim in travelling to Myanmar was "to first of all, demonstrate my sympathy to the people and government at this time of crisis and challenge, and to see for myself the situation on the ground."
Ban said he hoped to set up a "logistics hub" to coordinate international aid, either in Myanmar or in the region, and that the United Nations and the Association of Southeast Asian Nations could jointly assign a coordinator.
Ban said that Myanmar agreed to allow Asian relief workers "under the auspices of ASEAN, to oversee and begin distributing international aid supplies.
"We have received government permission to operate nine WFP helicopters, which will allow us to reach areas that have so far been largely inaccessible.
Ban said he believed that "further similar moves will follow -- including expediting the visas of relief workers seeking to enter the country. I am confident that emergency relief efforts can be scaled up quickly."
During the visit Ban said he hoped to meet with Senior General Than Shwe and other top government officials -- although he has failed so far to get the reclusive junta leader even to take his telephone calls.
"My role and the role of the United Nations, working closely with ASEAN and the government of Myanmar, will be to ensure that all these efforts are well coordinated and as effective as they can be under these difficult circumstances."
"I will do my utmost for the people of Myanmar," the UN chief said.
Myanmar began three days of mourning Tuesday for 133,000 people dead or missing from Cyclone Nargis, which hit May 3.
With survivors still desperate for help, global pressure is mounting on the regime to do more for the storm victims. Myanmar agreed at regional talks Monday in Singapore to allow neighboring countries to coordinate an international relief effort.
But doubts emerged over how effective any relief effort would be, since the junta has refused to allow in foreign aid workers in anything like the numbers needed, despite warnings that people could die without help.
The United Nations, which estimates that only 500,000 of the 2.4 million affected by the storm are receiving aid, is making a top-level diplomatic effort to press the regime to open up the country.
Noting some progress in that regard, Ban said the junta had now authorized the World Food Program to begin deliveries with nine helicopters.
Ban will spend two days in Myanmar Thursday and Friday, before returning to Bangkok for a series of bilateral meetings Saturday. He is scheduled to meet with Thai Prime Minister Samak Sundaravej and Foreign Minister Noppadon Pattama, Ban said.
He goes back to Yangon Sunday for a fundraising conference organized jointly by the United Nations and ASEAN, then is scheduled to return to New York Monday.