By AFP and Focus | 2026-06-03

MANILA -- The Philippines and Vietnam declared peace, stability, and freedom of navigation in the South China Sea "nonnegotiable" as the two claimant states upgraded their ties to an Enhanced Strategic Partnership and renewed a key defense cooperation agreement.

The agreement was announced June 1 during Vietnamese President To Lam's state visit to Manila, where he and Philippine President Ferdinand Marcos Jr. elevated their countries' relations to an Enhanced Strategic Partnership.

The upgraded framework is expected to broaden cooperation in security, trade, technology and people-to-people exchanges. Vietnam is Manila's only strategic partner within the ASEAN bloc, with the two countries marking 50 years of diplomatic relations in 2026.

The partnership has become increasingly important as the region faces an "uncertain global environment," said Marcos. He cited geopolitical fragmentation, supply chain pressures, trade strains and emerging technologies.

S. China Sea cooperation

Manila and Hanoi are among several governments, including Beijing, that claim parts of the Spratly Islands, a chain near vital shipping lanes and resource-rich waters.

The Philippines and Vietnam agree that maritime stability remain central to their partnership, Marcos said at a joint news conference.

"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," he said.

Manila and Hanoi remain committed to resolving disputes peacefully and in accordance with international law, including the 1982 United Nations Convention on the Law of the Sea (UNCLOS) and a 2016 South China Sea arbitral ruling, said Marcos.

"We stand resolute in our commitment to the peaceful resolution of disputes, grounded firmly in international law," he said.

The 2016 ruling invalidated China's sweeping claims over most of the South China Sea and upheld the Philippines' maritime entitlements under UNCLOS. Beijing rejects the decision.

Under the renewed 2010 defense cooperation agreement, the Philippines and Vietnam agreed to continue security and defense delegation exchanges and step up information-sharing. The pact will support cooperation in maritime security, military education and disaster risk reduction and management, Philippine state media said.

The countries already have expanded practical maritime cooperation, conducting their first joint coast guard exercises in 2024 despite overlapping claims in the disputed waters.

The leaders witnessed the signing of agreements covering digital development and tourism, while pledging closer law enforcement coordination against transnational crime.

The two governments agreed to strengthen cooperation against cyber scams, illegal migration, human trafficking and illegal gambling. Any individual or organization using the territory of one country to carry out sabotage against the other will be prevented, said Lam.

A focus on economics

Beyond security, observers expect the upgraded partnership to support economic cooperation and supply chain resilience. Vietnam is a major supplier of rice to the Philippines, while Hanoi is seeking wider market access for its products.

The upgrade reflects Vietnam's "bamboo diplomacy," Mark Manantan, a research fellow at La Trobe University's Centre for Global Security, told Nikkei Asia. Under that strategy, Hanoi seeks to play a more active role in shaping the regional agenda while maintaining diverse partnerships.

Closer ties with Manila could indirectly strengthen Hanoi's engagement with Philippine partners such as the United States and Japan, added Manantan.

Chester Cabalza, president of the International Development and Security Cooperation think tank, told Nikkei Asia the partnership upgrade represents a significant step toward closer security alignment between two Southeast Asian middle powers. Stronger ties could help both countries respond to Chinese "gray zone activities" while preserving their strategic autonomy, he said.

"Gray zone" refers to acts that stop short of war but tax a country's security forces.

The upgraded partnership comes against a wider backdrop of growing concern over military and coast guard activity in the South China Sea.

Days earlier, China's military said it drove away a Dutch navy vessel it accused of illegally entering waters around the Paracel Islands, while the Netherlands said its frigate had been operating in international waters.

The United States, India, Japan and Australia subsequently voiced concern over developments in the South and East China seas, criticizing dangerous military maneuvers and blocking actions without naming China.