MANILA, Philippines (AP) — U.S. Secretary of State Antony Blinken called on China to comply with a 2016 arbitration ruling that invalidated Beijing’s vast territorial claims in the South China Sea and warned that Washington is obligated to defend treaty ally Philippines if its forces, vessels or aircraft come under attack in the disputed waters.

Blinken’s statement, issued by the U.S. Embassy in Manila on Tuesday, was released on the sixth anniversary of the 2016 decision by an arbitration tribunal set up in The Hague under the U.N. Convention on the Law of the Sea after the Philippine government complained in 2013 about China’s increasingly aggressive actions in the disputed waters.

China did not participate in the arbitration, rejected its ruling as a sham and continues to defy it, bringing it into territorial spats with the Philippines and other Southeast Asian claimant states in recent years.

“We call again on the PRC to abide by its obligations under international law and cease its provocative behavior,” Blinken said, using the acronym for China’s formal name, the People’s Republic of China.

“We also reaffirm that an armed attack on Philippine armed forces, public vessels, or aircraft in the South China Sea would invoke U.S. mutual defense commitments” under the 1951 U.S.-Philippines Mutual Defense Treaty, Blinken said.

There was no immediate reaction from Beijing. But Chinese Foreign Minister Wang Yi told a news conference in Malaysia’s administrative capital of Putrajaya that China is speeding up talks with the Association of Southeast Asian Nations, which includes the Philippines and three other claimant states, to come up with a nonaggression pact called a “code of conduct” to turn the South China Sea “into a sea of peace and cooperation.”

“We will oppose bloc confrontation and Cold War mentality,” Wang told journalists after meeting his counterpart in Malaysia, the last stop in his five-nation swing through Southeast Asia. He did not take any questions.

In addition to China and the Philippines, Vietnam, Malaysia, Taiwan and Brunei have had overlapping claims in the busy waterway, where an estimated $5 trillion in goods passes each year and which is believed to be rich in undersea gas and oil deposits.

The potential flashpoint has become a key front of U.S.-China rivalry.

Washington lays no claim to the disputed waters but has deployed Navy ships and Air Force jets to patrol the waterway for decades and says freedom of navigation and overflight is in the U.S. national interest. That has provoked angry reactions from China, which has accused the U.S. of meddling in a purely Asian dispute and warned it to stay away.

Philippine Foreign Secretary Enrique Manalo said Tuesday that the arbitration ruling will be a pillar of his new government’s policy and actions in the disputed region and rejected attempts to undermine the “indisputable” decision.

“These findings are no longer within the reach of denial and rebuttal and are conclusive as they are indisputable. The award is final,” Manalo said in a statement.

“We firmly reject attempts to undermine it … even erase it from law, history and our collective memories,” said Manalo, who did not directly name China.

New Philippine President Ferdinand Marcos Jr. took office June 30 after a landslide electoral victory.

Marcos Jr.’s predecessor, Rodrigo Duterte, put the arbitration ruling on the backburner for years after taking office in 2016 and nurtured cozy ties with Chinese President Xi Jinping while criticizing U.S. security policies.

In 2019, Duterte said he finally asked Xi to comply with the ruling but was flatly told, “We will not budge.”

Marcos Jr. has upheld the arbitration ruling and said he would not allow even one “square millimeter” of Philippine waters to be trampled upon.

But he said in January before winning the presidency that since China has refused to recognize the ruling, Duterte’s policy of diplomatic engagement is “really our only option.”

Dozens of left-wing activists and workers protested in front of the Chinese Consulate in Manila’s Makati financial district on Tuesday, asking Beijing to respect the arbitration ruling and for Marcos Jr. to defend the country’s territory and sovereign rights in the South China Sea.

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Associated Press journalists Joeal Calupitan and Aaron Favila in Manila and Eileen Ng in Kuala Lumpur, Malaysia, contributed to this report.