MANILA: Manila’s defense pact with the US is an “untapped weapon” that will help maintain balance in the Asia Pacific region, the Philippine Senate’s security committee head said on Thursday, amid increasing claims from China in the South China Sea.

Sen. Panfilo Lacson’s comment followed US Secretary of State Antony Blinken’s phone conversation with Filipino Foreign Secretary Teodoro Locsin, Jr. on Thursday, during which the US reaffirmed its commitment to defend the Philippines in the event of armed attacks in the disputed South China Sea.

Blinken’s assurances came after Locsin said on Wednesday that the Philippines had filed a protest over Beijing’s new law allowing Chinese coast guards to open fire on foreign vessels to prevent threats to China’s “national sovereignty, sovereign rights, and jurisdiction” at sea.

China claims almost all of the South China Sea, a major oil-rich trade route, to which several Southeast Asian nations, including the Philippines, have overlapping claims.

“The US-PH Mutual Defense Treaty will help maintain the balance of power in the Asia-Pacific — including in the South China Sea,” Sen. Lacson said, as quoted in a statement released by the Philippine Senate Committee on National Defense and Security.

Under the deal signed by Washington and Manila in 1951 both nations would extend military support to each other if either of them is attacked by an external party.

“The US-PH Mutual Defense Treaty is one yet untapped weapon in our arsenal,” Lacson said, “I certainly hope we do not draw that weapon … We might as well keep it there.”

During his call with Locsin, Blinken also spoke of the importance of the military deal in US-Philippines ties.

“Secretary Blinken stressed the importance of the Mutual Defense Treaty (MDT) for the security of both nations, and its clear application to armed attacks against the Philippine armed forces, public vessels or aircraft in the Pacific, which includes the South China Sea,” the US State Department said in a statement.

“Secretary Blinken also underscored that the United States rejects China’s maritime claims in the South China Sea to the extent they exceed the maritime zones that China is permitted to claim under international law as reflected in the 1982 Law of the Sea Convention,” it said.

China’s new legislation, passed last week, has fueled an outcry in the Philippines. 

“When another country claims the oceans surrounding us, which we claim, even threatens to demolish our fishing boats or fishing boats of any country that get to that ocean or that sea, this is a serious cause for concern,” Sen. Richard Gordon told the Senate during a plenary meeting on Tuesday. “This is a shot in the bow of all the claimants in the territories,” he said.