The head of US forces in the Pacific reaffirmed American commitment to support the Philippines Monday, amid the country's continuing territorial dispute with China.

Admiral Samuel Locklear met with President Benigno Aquino and voiced his support in helping modernise the country's ill-equipped armed forces, considered to be among the weakest in the region, the presidential spokesman said.

Locklear "reaffirmed the long-standing partnership between the US and the Philippines," Aquino's spokesman Ramon Carandang told reporters.

The admiral also "reiterated the commitment of the US to help the Philippines establish a minimum credible defence", Carandang said.

The two officials discussed the South China Sea issue in "broad strokes" with no specific details given, Carandang said.

The Philippines, which has a mutual defence treaty with the United States, has been seeking greater support from its main defence ally after a face-off with China over the Scarborough Shoal in the South China Sea in April.

Locklear was due to meet with Filipino defence officials later Monday, in which he would discuss "domain awareness" amid a changing security climate, according to the US Department of Defense website.

"So what we are looking for is to try to provide [the Philippines] assistance that builds the interoperability of our defence forces over time," the website quoted him as saying.

He also warned that a possible "miscalculation" in the dispute could threaten regional stability and reiterated that the US and Philippine militaries needed to learn to work together better.

"I'm looking forward to giving the message to the Filipino military and to the leaders there that the United States is a very reliable ally. We want the Filipinos to be a reliable ally to us as well," he was quoted as saying.

Chinese-Philippine tensions have increased due to the standoff with the Philippines accusing China of "duplicity" and "intimidation" in a recent regional forum in Cambodia.

China claims the entire South China Sea as its historical territory, even up to the coasts of other Southeast Asian countries like the Philippines.