US Secretary of State Antony Blinken has been laying the groundwork for a trilateral summit with the Philippines and Japan next month in Washington.

He met his Philippine counterpart on Tuesday in Manila.

Blinken said the two sides share concerns about China's maritime actions, which threaten their common vision for a free and open Indo-Pacific, including the South China Sea.

He also mentioned a recent series of maritime confrontations between Manila and Beijing.

Philippine foreign secretary Enrique Manalo expressed thanks for Washington's support.

He said they discussed regional issues, especially the situation in the South China Sea, adding that his country is committed to managing disputes in accordance with the rules-based international order.

Blinken reaffirmed his country's commitment to a Mutual Defense Treaty, saying the pact extends to armed attacks against the Philippines anywhere in the South China Sea.

He also said the trilateral summit with Japan is aimed at improving regional stability.