US naval operations chief Admiral Michael Gilday made the remarks during a visit to the Southeast Asian nation, as part of US efforts to strengthen military alliances across the region and beyond.

Beijing's growing assertiveness on Taiwan and its building of bases in the contested South China Sea have given fresh impetus to Washington and Manila to repair their partnership.

Previous Philippine president Rodrigo Duterte favoured China over his country's former colonial master, but the new administration of Ferdinand Marcos has been keen to reverse that.

The longtime treaty allies agreed this month to resume joint patrols in the sea, and also struck a deal to give US troops access to another four military bases in the Philippines.

Gilday said the countries were "in the beginning of the planning stages" for combined maritime activities, but he insisted the United States was "committed and focused".

China claims sovereignty over almost the entire South China Sea, through which trillions of dollars in trade passes annually, and has ignored an international court ruling that its claims have no legal basis.

In Manila, Gilday held talks with Philippine navy chief Vice Admiral Toribio Adaci and military chief of staff General Andres Centino.

They agreed "in principle that we need to move forward, focused and with speed, in order to improve our interoperability together in the South China Sea and across the region", Gilday told reporters.

Given its proximity to Taiwan and its surrounding waters, cooperation from the Philippines would be key in the event of a conflict with China, which a four-star US Air Force general has warned could happen as early as 2025.

But Gilday told a US think-tank in October that the US military must be ready to respond to a potential invasion of Taiwan much sooner.

"I think my responsibilities as a navy chief are to make sure that we can field the most capable, ready and lethal force that we can around the world, including, obviously, the Indo-Pacific," Gilday said Wednesday, using an American term for the Asia-Pacific region.

Meanwhile, Chinese Foreign Minister Qin Gang said Wednesday in Indonesia that Beijing would work with Southeast Asian countries to protect peace and stability in the South China Sea.

While China claims nearly all of the sea, the Philippines, Vietnam, Malaysia and Brunei also have overlapping claims to parts of it.

Qin's remarks came less than two weeks after the Philippines accused a Chinese security vessel of using a military-grade laser light against a Philippine patrol boat.

Beijing has defended its actions, saying the Philippine boat "intruded" into China's sovereign waters without permission.

President Marcos insisted Saturday that the Philippines "will not lose one inch" of territory following the latest maritime incident between the two countries.