MANILA, April 2 (Reuters) - The Philippines, the world's top rice buyer, said on Thursday it has secured Vietnam's commitment for continuous supply of the staple foood, which may include a 300,000-tonne importation, under an existing bilateral trade agreement.

The announcement comes after Vietnam, the world's third-largest rice exporter, stopped signing new deals as it checks whether it has sufficient domestic supplies to cope during the coronavirus outbreak.

Agriculture Secretary William Dar said he had received a letter from Deputy Minister Le Quoc Doanh of Vietnam's Ministry of Agriculture and Development expressing Hanoi's commitment to honour its existing supply contracts with Philippine importers.

"The government of Vietnam always considers rice trading with the Philippines is not only of economic importance, but also of significance for our good diplomatic relations between the two nations," Le said in the letter, according to Dar.

The letter was sent after Dar early this week said about 1.38 million tonnes of rice imported by Philippine traders have yet to be delivered, including 1.25 million tonnes ordered from Vietnam.

Vietnamese Prime Minister Nguyen Xuan Phuc said on Tuesday his country needs to sell rice but exports must be controlled to ensure food security.

Dar has sought to allay concerns about a tightening of domestic supply at a time when many parts of the country have been locked down to contain the spread of the coronavirus, while the world's top rice exporters have also been hit by the pandemic.

"Le also said that Hanoi is also working on possible governmental agreement with Manila on rice trade," Dar said in a statement, without mentioning any volume.

The Philippine government this week said it was looking to import 300,000 tonnes of rice to ensure sufficient domestic supply of the staple while it seeks to contain the spread of the coronavirus in the Southeast Asian country.

(Reporting by Enrico dela Cruz; editing by Emelia Sithole-Matarise)