By Laura MacInnis

GENEVA, May 6 (Reuters) - Myanmar's military rulers are allowing in food and other emergency supplies but have not yet approved visas for some aid workers seeking to assess the damage from a massive cyclone, the United Nations said on Tuesday.

"So far the government is welcoming the material assistance. That assistance is on its way," Elisabeth Byrs, spokeswoman for the U.N. Office for the Coordination of Humanitarian Affairs, told a news conference in Geneva.

"We are waiting for the visas for our disaster management assessment team in Bangkok," Byrs said, expressing hope the staff would be permitted to travel to the former Burma soon.

There are already some U.N. workers in Myanmar, including small teams from the U.N. High Commissioner for Refugees (UNHCR) and the World Health Organisation (WHO) who are scrambling to help the survivors of Cyclone Nargis, Asia's worst since 1991.

Reinforcements from UNICEF and other agencies are awaiting visa approval from Myanmar. Byrs said Yangon's willingness to accept deliveries of tents, mosquito nets, water purification tablets, health kits and other items was "a good sign."

BLOCKED ROADS

The death toll climbed to 22,464 and an additional 41,000 people were missing, state media reported on Tuesday, as a result of the cyclone which hit Myanmar's Irrawaddy delta and triggered a tidal wave that left people nowhere to run. The storm surge was reported to have been 12 feet (3.5 metres) high.

The disaster has thrust isolated Myanmar back into the world spotlight, following the government's heavy-handed repression of pro-democracy protests that drew condemnation from the U.N. Human Rights Council and several Western capitals.

The United Nations, which is trying to calculate how much money donor governments should provide for Myanmar, said floods, debris and fallen power lines were impeding access to the hardest hit areas, which also lost their telephone services.

"Efforts to carry out a comprehensive assessment continue to be hindered by the lack of communications and blocked roads," Byrs said. "The most affected regions are only accessible by helicopter."

About 24 million people -- nearly half Myanmar's population -- live in disaster-struck areas of the country neighbouring India, China, Thailand and Laos.

The U.N. has estimated that several hundred thousand are without shelter and safe drinking water, and International Federation of the Red Cross spokesman Eric Porterfield said his organisation anticipates more than 1 million people could be made homeless as a result of the storm.

Aid agencies also said the destruction could spark epidemics of water- and food-borne diseases, such as diarrhoea and cholera, and hinder efforts to fight malaria, tuberculosis and other ailments requiring routine vaccinations and medicines.

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