The United States is increasing its military presence in the Philippines, gaining access to four more sites and strengthening the Southeast Asian nation’s role as a key strategic partner for Washington in the event of a conflict with China over Taiwan.
The agreement, announced on Thursday, allows Washington to position military equipment and rotate its troops through nine locations controlled by the Philippines, marking the first time in 30 years that the United States will have such a large military presence in the country.
The deal comes as Washington has tried to reaffirm its influence in the region as part of a broader effort to counter Chinese aggression, reinforcing partnerships with strategic allies and bolstering relations that have soured in recent years. Fears have also grown over a possible Chinese invasion of Taiwan, the island democracy that China claims as its territory. Among the five treaty allies that the United States has in Asia, the Philippines and Japan are the most geographically close to Taiwan, with the Philippines’ northernmost island of Itbayat just 93 miles away.
In a news conference on Thursday, Mao Ning, a spokeswoman for China’s foreign ministry, accused the United States of threatening regional peace and stability with its announcement.
“Out of self-interest, the United States continues to strengthen its military deployment in the region with a zero-sum mentality, which is exacerbating tension in the region and endangering regional peace and stability,” she said. “Countries in the region should remain vigilant against this and avoid being coerced and used by the United States.”
In a news conference, the U.S. defense secretary, Lloyd J. Austin III, stressed that these new sites were not permanent.
“This is an opportunity to increase our effectiveness, increase interoperability,” he said during a trip to Manila that began on Tuesday. “It is not about permanent basing, but it is a big deal. It’s a really big deal.”
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Carlito Galvez Jr., the Philippines’ defense secretary, declined to name the locations of the four additional sites, saying the government needed to consult local officials first. American officials have long eyed access to the Philippines’ northern territory, such as the land mass of Luzon, as a way to counter China in the event that it attacks Taiwan.
In November, Lt. Gen. Bartolome Vicente Bacarro of the Philippines said that Washington had identified five possible sites, including two in Cagayan, one in Palawan, one in Zambales and one in Isabela. Cagayan and Isabela are in the northern part of the Philippines, with Cagayan sitting across from Taiwan.
“Having increased U.S. access in Northern Luzon, close to Taiwan, is really ensuring that the Philippines and the U.S. alliance is going to have a front and center role in Northeast Asian security and deterrence,” said Drew Thompson, a visiting senior research fellow at the Lee Kuan Yew School of Public Policy at the National University of Singapore and a former U.S. defense official.
The Philippines is the United States’ oldest treaty ally in Asia. Washington is shoring up its presence in the country after relations deteriorated during former President Rodrigo Duterte’s six-year term, which ended last year.
During Mr. Duterte’s term, he frequently criticized Washington and complained that the United States, the Philippines’ former colonial ruler, had created defense treaty agreements that weighed heavily in favor of the Americans.
U.S. officials were concerned when Mr. Duterte threatened to scrap the Visiting Forces Agreement, a long-held defense pact that allows for large-scale joint military exercises between the two allies. He also threatened to disregard the Enhanced Defense Cooperation Agreement, the deal that formed the basis for Thursday’s announcement.
Since he took office last June, President Ferdinand Marcos Jr. has sought to revive his country’s relationship with the United States, surprising many foreign policy experts. On the campaign trail, Mr. Marcos had indicated that he would try to forge closer ties with China, a hallmark of Mr. Duterte’s term.
Mr. Marcos, the son of former dictator Ferdinand E. Marcos, has since said he “cannot see the Philippines in the future without having the United States as a partner.” At least 16,000 Filipino and American troops will train side by side in the northern province of Ilocos Norte, the stronghold of the Marcos family, later this year.
Under Mr. Marcos, officials in the Philippines have started building contingency plans for a possible Chinese invasion of Taiwan. When the former House speaker Nancy Pelosi visited Taiwan last August, China responded by launching military exercises in multiple areas, including the Bashi Channel, a waterway separating Taiwan and the Philippines.
Taiwanese officials called it an “air and sea blockade.”
If war were to break out over Taiwan, “the battle space will encompass the Philippines,” said Mr. Thompson. China’s moves in the Bashi Channel “really brought that home for Philippine leaders,” he added.
The Philippines is also strategically important because of what lies beneath the surface of the ocean. The waters just off the west coast that abut the South China Sea — where China has turned a series of sand mounds into military bases — are flush with undergrowth, making it ideal for stealth submarine movement.
“You need to control the Philippines because of submarines,” said Michael J. Green, an Asia expert on the National Security Council under George W. Bush who now heads the United States Studies Center at the University of Sydney. “If you can picture it, the undersea topography is jungle-y — you can sneak in submarines.”
The U.S. Marine Corps has proposed shifting toward smaller units in the region that could deploy to remote islands for missile attacks, rear support, counterattacks or intelligence gathering in the case of a war with China over Taiwan. Along with islands in Japan, the islands of the Philippines represent what American military planners see as one of the most important locations for such tactics.
“I would expect to see rotational access and more frequent deployments of these small marine teams for training and joint exercises alongside their Philippine counterparts,” said Gregory B. Poling, a senior fellow for Southeast Asia and director of the Asia Maritime Transparency Initiative at the Center for Strategic and International Studies in Washington.
Three decades ago, the U.S. presence in the Philippines was a sore point among many Filipinos. The military bases maintained by Washington for nearly a century were seen to be a vestige of American colonialism. In 1992, the United States had to shut down its last American base in the Philippines after street protests and a decision to get rid of it by the Philippine Senate.
But as China began its military incursions in the South China Sea, public opinion on the American presence in the Philippines has shifted.
The Philippines now hopes to get American support to fend off Beijing’s continued military buildup in the South China Sea. Manila and Beijing have been locked in a long-running disagreement over the disputed waters that both sides claim as their own.
Among some quarters, the planned increase of the American military presence in the Philippines remains contentious. In a statement, Renato Reyes, secretary-general of the nationalist activist political group Bayan, said Filipinos “must not allow our country to be used as staging ground for any U.S. military intervention in the region.”
“Allowing U.S. use of our facilities will drag us into this conflict, which is not aligned with our national interests,” Mr. Reyes said.
Jason Gutierrez contributed reporting from Manila, and Damien Cave from Sydney.