The United States said on Monday that it would not take sides in the Huangyan Island standoff between China and the Philippines in the South China Sea and reiterated support for a diplomatic resolution to the territorial dispute.

Washington does not take sides on competing sovereignty claims there, but has a national interest in maintaining freedom of navigation as well as peace and stability, US Secretary of State Hillary Clinton said, after meeting top diplomatic and defense officials from the Philippines.

Philippine Foreign Secretary Alberto del Rosario and Defense Secretary Voltaire Gazmin attended the 2+2 dialogue with their US counterparts, Clinton and Leon Panetta, in Washington.

"The United States supports a collaborative diplomatic process by all those involved for resolving the various disputes that they encounter," Clinton said. "We oppose the threat or use of force by any party to advance its claims."

Gazmin alluded to tension with China over islands in the South China Sea as he called for the need to "intensify our mutual trust to uphold maritime security and the freedom of navigation".

"We should be able to work together to build a minimum, credible defense posture for the Philippines, especially in upholding maritime security," Gazmin said.

The Philippines and China have been embroiled in the Huangyan Island dispute, with both nations stationing vessels there for nearly three weeks to assert their sovereignty.

China on Monday highlighted remarks made by the Philippine president about de-escalating the tension over the island, urging the Philippines to "match its words with deeds" and return to the proper pathway of diplomatic solutions.

Speaking of the tension, Philippine President Benigno Simeon Cojuangco Aquino III said he had issued instructions to his military, telling them not to intensify the issue.

Chinese Foreign Ministry spokesman Liu Weimin stressed that there is no change in China's stance of using diplomatic channels to peacefully resolve the issue, which was triggered when a Philippine warship harassed Chinese fishermen and raised concerns over China's sovereignty of the island.

The Philippine officials also stressed diplomacy when asked what aid they had requested from Washington, saying that Manila sought to bring the South China Sea issue to international legal bodies.

Clinton reaffirmed the US commitment to the 60-year-old Mutual Defense Treaty with the Philippines, calling the Philippines a country "at the heart" of the new US strategy toward the Asia-Pacific.

Washington would help improve the Philippines' "maritime presence and capabilities" with the transfer of a second high-endurance (coast guard) cutter this year, Panetta said.

The US emphasis on neutrality and a diplomatic resolution would encourage Manila to be more restrained on the Huangyan Island issue, said Fan Jishe, a US studies expert at the Chinese Academy of Social Sciences.

"Washington doesn't want territorial disputes between its Asian allies and China to be obstacles to China-US relations," he said.