The Philippines and Vietnam will agree to boost coastguard cooperation during a visit to Hanoi next week by Philippine President Ferdinand Marcos Jr, officials said, a move that risks angering China.

The two Southeast Asian countries have competing claims over swathes of the South China Sea, an important waterway for fishing and global trade that China claims almost in its entirety.

The two countries will sign a memorandum of understanding on cooperation between their coastguard forces, the Philippine coastguard said on Thursday.

It is unclear what the agreement will entail, but coastguard cooperation is crucial to reducing the risk of clashes between fishing vessels that encroach into foreign waters - a step that could help ease bilateral territorial disputes.

China, with its vast claims to the South China Sea, tends to view progress in the resolution of border disputes among other claimants with scepticism.

After Vietnam and Indonesia recognised the boundaries of their respective Exclusive Economic Zones (EEZs) in the South China Sea in December 2022, China's coastguard repeatedly sailed close to those strategic areas triggering angry reactions from both Jakarta and Hanoi.

China's response however could be muted in this case because the deal is not about recognition of maritime claims, said Phan Xuan Dung, researcher on Vietnam at the Singapore-based ISEAS think tank.

Marcos will meet Vietnamese leaders on a two-day visit starting on Monday, Vietnam's foreign ministry spokeswoman said on Thursday, noting the countries had close ties in multiple fields including defence and security.

In November, Marcos said the Philippines had approached Vietnam and other neighbours to discuss a separate code of conduct for the South China Sea, another move that would irk China which has been promoting a broader regional pact for years without success.

The two countries are also expected to boost their cooperation on rice supplies, according to a Philippine official, with the Philippines being already the largest market for Vietnam's exports.

"The two most promising areas of cooperation between the Philippines and Vietnam are food security and maritime security," Alexander Vuving, of the Hawaii-based Inouye Asia-Pacific Center for Security Studies, said.

"But Vietnam is far more cautious than the Philippines about not angering China" on maritime security, he added.

Vietnam's foreign ministry did not immediately reply to a request for comment about the expected agreement on coastguard cooperation.