The U.S. military will be expanding its presence in the Philippines as a key strategic footing for Washington amid the escalating China-Taiwan tensions.

On Thursday, U.S. Defense Secretary Llyod Austin arrived in Manila to meet with his Philippine counterpart Carlito Galvez Jr. as well as President Ferdinand Marcos Jr. to discuss both countries’ commitment to strengthening their forces to resist an armed attack.

As part of the agreement between the longtime allies, U.S. forces were granted access to four more military camps, ramping up to a total of nine bases throughout the Philippines. The expansion marks the first time in 30 years that the U.S. will hold a large military presence in the country.

Austin, who has strengthened security alliances in Asia amid China’s assertiveness toward Taiwan and territorial disputes in the South China Sea, assured the Southeast Asian nation of U.S. military support.

The Philippines is Washington’s oldest treaty ally in Asia. The 1951 Mutual Defense Treaty obligates both countries to help defend each other in events of major conflicts.

“That’s just part of our efforts to modernize our alliance,” Austin said at a joint press conference with Philippine Secretary of National Defense Carlito Galvez. “And these efforts are especially important as the People’s Republic of China continues to advance its illegitimate claims in the West Philippine Sea.

Although Austin did not disclose the location of the new bases, the U.S. previously sought access to military camps in the northern region of Luzon, which is across a sea border from Taiwan.

Austin noted that new bases were not permanent. 

“This is an opportunity to increase our effectiveness, increase interoperability,” he said. “It is not about permanent basing, but it is a big deal. It’s a really big deal.”

Although the Philippine Constitution prohibits foreign troops from being permanently based in the country, the countries’ Enhanced Defense Cooperation Agreement (EDCA) allows visiting U.S. forces to indefinitely stay in buildings they construct within designated camps along with their defense equipment, except for nuclear weapons.

“I have always said that it seems to me that the future of the Philippines and for that matter the Asia-Pacific will always have to involve the United States simply because those partnerships are so strong,” Marcos reportedly told Austin during their meeting.

On Thursday, Chinese Foreign Ministry spokesperson Mao Ning accused the U.S. of pursuing its “selfish agenda” and said the Philippines’ decision undermines regional stability with the new arrangement.

“China has always consistently believed that defense and security cooperation among countries should be conducive to regional peace and stability, and should not target or harm the interests of third parties,” he said.

He added, “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. Countries in the region should remain vigilant against this and avoid being coerced and used by the United States.”

On the same day, leftist activists held a protest outside the main military camp where Austin met with his Philippine counterpart. 

While protesters held signs stating, “Junk EDCA,” some Filipinos set a mock U.S. flag ablaze.

The leftist groups and nationalists protested against the U.S. military presence in the former American colony, saying that the agreement will further cause tensions.

“Additional troops in the Philippines run counter to the cause of peace. It will further escalate the military tensions in the region and will drag the Philippines into possibly a shooting war. Nobody wants that,” protest leader Teodoro Casino told AP News.

“[Filipinos] must not allow our country to be used as a staging ground for any U.S. military intervention in the region,” Renato Reyes, the secretary-general of the nationalist activist group Bayan, told The New York Times. “Allowing U.S. use of our facilities will drag us into this conflict, which is not aligned with our national interests.”

The Philippines previously hosted two of the world’s largest U.S. Navy and Air Force bases, which were shut down in the early 1990s after the Philippine Senate rejected an extension.

However, American forces later returned for combat exercises with Filipino troops.

At least 16,000 Filipino and American troops will reportedly train together in the northern province of Ilocos Norte later this year.

“I am confident that we will continue to work together to defend our shared values of freedom, democracy and human dignity,” Austin said. “As you heard me say before, the United States and the Philippines are more than just allies. We’re family.”