"The World Food Programme has halted aid shipments to Burma after the contents of its first delivery were impounded on arrival in the military-ruled country.
The UN body says the Burmese government seized aid material flown in to help victims of Cyclone Nargis, which has killed tens of thousands.
The WFP said it had no choice but to halt aid until the matter was resolved.
Burma's ruling generals have faced mounting criticism over their handling of the crisis.
The UN fears more than 1.5 million people have been affected by the cyclone, with tens of thousands made homeless and vulnerable to disease.
Burmese state media say 22,980 people were killed, but there are fears the figure could rise to 100,000.
Hundreds of thousands of people have no food, water or shelter. International aid agencies on the ground say they have reached only 10% of those that need help.
Despite this, Burma's foreign ministry issued a statement on Friday saying it was not ready to allow foreign aid workers to enter the country.
The junta said it was happy to accept aid, but insisted it would control the distribution itself."
"Tanto el cólera como la malaria están empezando a aparecer en la región del delta, donde el ciclón ha creado todas las condiciones para una epidemia.Outbreaks of cholera and malaria are also being reported in the delta region, where the cyclone created all the conditions for epidemics.
"Most of the area is covered by dirty water,” said Osamu Kunii. “There are a lot of dead bodies and the people there have very poor access—sometimes no access—to clean drinking water or food."
One Rangoon source said: “It is very difficult to bury the dead because everywhere is flooded. We needed expert relief workers.”