The Philippines has given its state grain agency the option to import an additional 350,000 tons of milled rice this year to keep domestic prices stable, a government source said on Monday.

An inter-agency committee would determine if there was really a need for additional imports and when the option should be taken, the source who has knowledge of the plan told Reuters.

Key to the decision would be first half grain output, the source added.

The Southeast Asian nation has also allocated up to 400,000 tons of rice import rights to private firms this year, up from a previous allotment of 300,000 tons, the same source said.

The Philippines, the world's biggest rice importer, earlier signed a deal to buy 1.5 million tons of milled rice from Vietnam, with shipments of the entire volume expected to be completed in July.

The deal was part of a total 1.8 million tons of rice Manila was earlier aiming to buy overseas this year, with the rest to be taken up by the private sector.