WASHINGTON — President Joe Biden has vowed that the US will defend the Philippines from any attack in the South China Sea, calling its support for Manila "ironclad".

Biden's comments come amid regular skirmishes and rising tensions between Chinese and Philippine coast guard vessels in the disputed waterway.

The US and the Philippines have had a mutual defense treaty in place since 1951.

China has repeatedly blamed the US for raising tensions in the region.

Speaking at the start of three-way talks at the White House with Japanese Prime Minister Fumio Kishida and Philippine President Ferdinand Marcos Jr, Biden said that "any attack on Philippine aircraft, vessels or armed forces in the South China Sea would invoke our mutual defense treaty".

Marcos's visit to Washington comes several days after his country accused a Chinese vessel of "highly dangerous maneuvers" near the Second Thomas Shoal, a disputed maritime region near the Spratly Islands.

The incident is one of several in which Chinese ships have been accused of harassment in the area, which has included firing water cannons and ramming Philippine ships.

While the three leaders did not specify China by name, Marcos said that they share an "unwavering commitment to the rules-based international order."

China, for its part, has repeatedly shrugged off criticism of its actions in the South China Sea and blamed the US for inflaming tensions in the Indo-Pacific.

"No one should violate China's territorial sovereignty and maritime rights and interests, and China remains steadfast in safeguarding our lawful rights," Chinese foreign ministry spokeswoman Mao Ning said on Thursday.

According to the White House and Japan's foreign ministry, the three countries plan to advance "trilateral defence cooperation", including through joint naval exercises.

The trilateral meeting comes one day after Biden and Kishida announced a raft of agreements between the US and Japan, focused in large part on strengthening defence ties in the face of a potential threat from China.

Those plans include an an expanded air defence network incorporating Australia, as well as a joint command structure between the US and Japan.

Additionally, US and Japanese forces will participate in three-way military exercises with the UK.

Speaking to reporters on Wednesday, Kishida acknowledged that the US and Japan would respond to "challenges" from China, even if they hope to continue "our dialogue with China and co-operating with China on common challenges". — BBC