CEBU, Philippines -- Defense chiefs from ASEAN member countries and key partners kicked off two days of talks on Wednesday, with the presence of top U.S., Indian, Japanese and Australian officials drawing attention to another political bloc.

High-profile attendees include U.S. Pentagon chief Pete Hegseth, Australian Deputy Prime Minister Richard Marles, Japanese Defense Minister Shinjiro Koizumi and Indian Defence Minister Rajnath Singh. The four countries are members of the Quad security grouping, meant to counter China's expanding influence in the Indo-Pacific.

They are among eight formal dialogue partners ASEAN invited to the gathering in the central Philippine city of Cebu. China is only sending a defense attache to the ASEAN Defense Ministers Meeting (ADMM).

The gathering comes amid tensions between China and the Philippines regarding the South China Sea, with recent encounters involving coast guard vessels from both nations risking escalation in a long-simmering territorial row. Manila and Beijing have also traded verbal barbs over Beijing's aggressive claim to nearly the entire South China Sea.

The Philippine Department of National Defense said in a statement on Tuesday that regional security issues, including maritime law enforcement and domain awareness, top the agenda in Cebu.

"Through its 2026 ASEAN chairship, the Philippines seeks to strengthen regional partnerships, sustain meaningful dialogue, and advance practical defense cooperation in support of a peaceful, secure, and stable Indo-Pacific region," the department said.

The defense officials will also discuss the security of critical underwater infrastructure -- including undersea fiber-optic communications cables and offshore energy grids -- amid heightened global concerns over sabotage and other deliberate disruptions, the department added.

Lingering tensions from last year's Cambodia-Thailand border clashes will also be discussed. The Armed Forces of the Philippines recently conducted a site visit to the Boeung Trakuon border crossing in Cambodia's Banteay Meanchey province as part of regional de-escalation efforts.

The Philippines is expected to press for a binding ASEAN-China Code of Conduct on the South China Sea by December. Negotiations that formally began in 2018 have dragged on, with differences remaining over where the code would apply.

Mark Manantan, research fellow with La Trobe University's Centre for Global Security, said the most meaningful outcomes from Cebu will likely be "practical cooperation on maritime security, underwater infrastructure, information-sharing and regional crisis management."

"I would temper expectations of any major breakthrough on the South China Sea," he told Nikkei Asia. "ASEAN members have different threat perceptions and strategic relationships with China, which will constrain how far the grouping can go in adopting stronger collective positions."

Defense officials are also expected to discuss potential spillover from the Middle East conflict, which has roiled the global economy. Manantan noted, though, that Manila is "under pressure to maintain its credibility as an impartial regional convenor while deepening its security relationships" with the four Quad members.

"This will be an important diplomatic test," he said. "The Philippines must demonstrate that its closer alignment with Quad countries does not undermine ASEAN centrality or turn the ADMM into another arena for U.S.-China strategic competition." The Quad defense chiefs are expected to draw attention as they are to hold bilateral and multilateral talks.

Julio Amador, CEO of Amador Research Services in Manila, says he expects the Quad members to use the ASEAN platform to meet. "And I think that is crucial," he told Nikkei Asia, "because we have not heard about the Quad for the longest time." The defense chiefs are gathering ahead of a summit next month, when ASEAN leaders and those of its major partners will meet in Manila.