MANILA--Defense Secretary Lloyd Austin is in the Philippines on Wednesday for talks about deploying U.S. forces and weapons in more Philippine military camps to ramp up deterrence against China’s increasingly aggressive actions toward Taiwan and in the disputed South China Sea.

Austin flew Tuesday night to Manila from South Korea, where he met his counterpart and said the U.S. would increase its deployment of advanced weapons such as fighter jets and bombers to the Korean Peninsula to bolster joint training with South Korean forces in response to North Korea’s growing nuclear threat.

The Philippines, Washington’s oldest treaty ally in Asia, has been a key front in the U.S. battle against terrorism, especially after the Sept. 11, 2001, attacks. Austin was scheduled to meet a small contingent of U.S. counterterrorism forces on Wednesday in the south, where they have provided intelligence and combat advice for years to Filipino troops battling a decadeslong Muslim insurgency, which has considerably eased but remains a key threat.

More recently, U.S. forces have intensified and broadened joint training for combat readiness and disaster response with Filipino troops in the Southeast Asian nation’s western coast, which faces the South China Sea, and in its northern Luzon region across the sea from the Taiwan Strait.

American forces have been granted access to five Philippine military camps, where they could stay indefinitely in rotating batches under a 2014 defense pact called the Enhanced Defense Cooperation Agreement.

In October, the U.S. sought access to a larger number of its forces and weapons to an additional five Philippine military camps, mostly in the main northern Luzon region, under the 2014 EDCA. That request would be high on the agenda for Austin’s meetings in the Philippines, according to Philippine officials.

“The visit of Secretary Austin definitely, obviously will have to do with many of the ongoing discussions on the EDCA sites,” Philippine Ambassador to Washington Jose Romualdez said at a news briefing Tuesday in the capital Manila.

Austin would hold talks Thursday with his Philippine defense counterpart, Carlito Galvez Jr., and National Security Adviser Eduardo Ano, Romualdez said. Austin would separately call on President Ferdinand Marcos Jr., who took office in June and has since taken steps to boost relations with Washington.

The U.S. defense chief is the latest American leader to visit the Philippines after Vice President Kamala Harris, who flew to the country in November in a sign of warming ties after a strained period under Marcos’s predecessor, Rodrigo Duterte.

During his time at the country’s helm from 2016, Duterte nurtured cozy ties with China and Russia while he threatened to sever ties with Washington, kick visiting American forces out and abrogate a major defense pact that allows thousands of U.S. forces to visit each year for large-scale combat training.

Romualdez said the Philippines needed to cooperate with Washington militarily to deter any escalation of tensions between China and Taiwan--not only because of the treaty alliance but to help prevent a major conflict.

“We’re in a Catch-22 situation. If China makes a move on Taiwan militarily, we’ll be affected--and all ASEAN region, but mostly us, Japan and South Korea,” Romualdez told The Associated Press, referring to the Association of Southeast Asian Nations, the 10-nation regional bloc that includes the Philippines.

The Philippines and ASEAN state members Brunei, Malaysia and Vietnam, along with Taiwan, have long been locked in increasingly tense territorial disputes with China in the South China Sea. The U.S. has been regarded as a crucial counterweight to China in the region and has pledged to come to the defense of the Philippines if Filipino forces, ships or aircraft come under attack in the contested waters.

The Philippines used to host two of the largest U.S. Navy and Air Force bases outside the American mainland. The bases were shut down in the early 1990s after the Philippine Senate rejected an extension, but American forces returned for large-scale combat exercises with Filipino troops under a 1999 Visiting Forces Agreement.

In 2014, the allies signed the EDCA, which allows larger numbers of American forces to stay in rotating batches within Philippine military camps, where they can build warehouses, living quarters, joint training facilities and store combat equipment, except nuclear arms. The Philippine Constitution prohibits the permanent basing of foreign troops and their involvement in local combat.