Marcos will meet Tuesday with President Donald Trump, who has rattled many European allies by demanding they pay more to be protected as part of NATO.

Both Defense Secretary Pete Hegseth and Secretary of State Marco Rubio, who have both identified China as a top threat, stated their commitment to the seven-decade treaty with the Philippines as they held separate meetings with Marcos on Monday.

"Together we remain committed to the Mutual Defense Treaty. And this pact extends to armed attacks on our armed forces, aircraft or public vessels, including our Coast Guard anywhere in the Pacific, including the South China Sea," Hegseth told Marcos.

Noting growing US defense spending, Hegseth said that the two countries "must forge a strong shield of real deterrence for peace, ensuring the long-term security and prosperity for our nations."

"We do not seek confrontation, but we are and will be ready and resolute," Hegseth said.

Marcos welcomed US support, noting the "changing political geopolitical forces and the political developments around our part of the world."

China and the Philippines have engaged in a series of confrontations in the contested waters, which Beijing claims almost entirely, despite an international ruling that the assertion has no legal basis.

Since his election in 2022, Marcos has boosted cooperation between the former US colony and the United States, both under Trump and his predecessor Joe Biden.