Flooding, which poured damaging salt water into paddy fields, could create long-term food insecurity for Myanmar and other poor Asian countries, World Food Programme spokesman Paul Risley warned.
The full extent of damage to rice supplies cannot be assessed yet because parts of the country have been cut off by flooding and damage to roads caused by Cyclone Nargis, which the government says has killed more than 15,000 people.
But Risley said that any disruption of rice supplies could be devastating.
"This year, while other Southeast Asian countries have been putting in place export bans and cutting rice exports, Myanmar has begun exporting to Sri Lanka and Bangladesh," he told AFP.
"So there are long-term concerns whether Myanmar can continue to maintain self-sufficiency and also whether they can continue commitments to other countries."
Any effect on exports would be felt sharply in other Asian countries where there are millions living in poverty as global prices for rice hi