Philippines and Vietnam Elevate South China Sea Stakes with Enhanced Strategic Partnership
MANILA — The Philippines and Vietnam declared peace, stability, and freedom of navigation in the South China Sea a “non-negotiable” position on Monday as the two Southeast Asian claimant states elevated their bilateral ties to an enhanced strategic partnership during Vietnamese President To Lam’s two-day state visit to Manila.
The agreement, announced following bilateral talks between President Ferdinand Marcos Jr. and President To Lam at Malacañang Palace, renews a 2010 defense cooperation pact and expands it to cover maritime security, military education, and disaster risk reduction. It marks the highest level of diplomatic engagement between the two nations and comes as the Philippines chairs the Association of Southeast Asian Nations for 2026.
Marcos and To Lam Forge New Defense Architecture
“As fellow claimant states, we reaffirm that maintaining peace, stability, and the freedom of navigation and overflight in the South China Sea remains non-negotiable,” Marcos said at a joint press conference following the talks. The statement drew direct comparison to the 2016 arbitral ruling that found China’s expansive “nine-dash line” claim over most of the disputed waters to be without legal basis.
Vietnam, which was not a party to the arbitration case, has nonetheless consistently championed adherence to international law and the 1982 United Nations Convention on the Law of the Sea in addressing maritime disputes. Both nations have faced escalating confrontations with Chinese vessels in the contested sea — the Philippines near Scarborough Shoal and Second Thomas Shoal, Vietnam near the Vanguard Bank and Paracel Islands.
To Lam described the Philippines as an “important regional partner” and said the two leaders agreed to closer coordination on both regional and global challenges. “We always want to bring the strategic partnership with the Philippines to a new high,” he said through an interpreter. The two governments signed additional bilateral agreements covering information technology, tourism, education, and combating transnational crimes including internet fraud, human trafficking, and illegal gambling.
ASEAN’s Binding South China Sea Code Takes Shape
The timing of the upgrade carries weight beyond bilateral optics. The Philippines assumed the ASEAN chairmanship this year with a mandate to finalize a binding South China Sea code with an enforcement mechanism — a first for the bloc. ASEAN foreign ministers endorsed the framework in May, setting the stage for negotiations with China on a legally grounded regime to replace the non-binding 2002 Declaration on the Conduct of Parties in the South China Sea.
Beijing has publicly resisted binding dispute mechanisms while quietly engaging in talks through senior officials. China’s Foreign Ministry warned that any enforcement language must respect “sovereign rights” under domestic law — a position ASEAN critics say is designed to legitimize the nine-dash line framework. The Philippines and Vietnam, as the two most vocal claimants challenging Beijing, presented a united front that analysts say strengthens ASEAN’s negotiating hand heading into the next round of code discussions.
Economically, Vietnam is the largest supplier of rice to the Philippines, a relationship both leaders pledged to deepen. Their coast guards held their first joint exercises in 2024 despite overlapping claims to some South China Sea features, a signal that economic and defense cooperation can proceed alongside unresolved territorial disputes.
Beyond bilateral ties, the enhanced partnership reflects a broader realignment across the Indo-Pacific. Japan and South Korea resumed their trilateral missile defense information-sharing framework with Australia last month. Australia and Vanuatu signed a security agreement in Port Moresby that explicitly bars foreign military bases in the Pacific. The United States has accelerated its Pacific deterrence schedule, with the Ronald Reagan carrier group conducting operations in the Philippine Sea and the Malabar Exercise expanding to include India for the first time in its 2026 edition.
Beijing rejected the 2016 arbitral ruling as null and void, asserting historical sovereignty over the waterway through which an estimated one-third of global maritime trade passes annually. Chinese naval and Coast Guard vessels have periodically interrupted Philippine and Vietnamese operations near contested features, including a high-seas confrontation last year in which Chinese personnel used water cannons against a Philippine resupply mission to Second Thomas Shoal.
