A Decade On, Manila and Hanoi Deepen Maritime Ties — A Quiet Check on Beijing in the West Philippine Sea

Article by J. Salazar

Published on July 21, 2026 12:00PM

Manila, Philippines — Ten years after an arbitral tribunal in The Hague under the United Nations Convention on the Law of the Sea (UNCLOS) rejected Beijing’s sweeping map-based claims, rival claimants continue to maneuver across the waters closest to the Philippines. With Vietnamese President To Lam visiting Manila last June 2026, Philippine President Ferdinand “Bongbong” Marcos Jr. signaled a clear intent to knit closer maritime cooperation with Hanoi, a move that could complicate Beijing’s approach in the West Philippine Sea. ¹ ⁴

“Maintaining peace, stability and the freedom of navigation and overflight in the South China Sea remains non‑negotiable,” Marcos told reporters during the state visit, adding that the two (2) countries were “resolute in their commitment to the peaceful resolution of disputes” and that this stance would be grounded in international law. The state visit upgraded ties to an “enhanced” strategic partnership and produced practical steps, an operational hotline and closer coastguard coordination aimed at preventing accidental clashes at sea. ²

Policy makers and maritime analysts see both symbolic and practical value in the Manila‑Hanoi alignment. Beijing’s traditional playbook has been to engage smaller claimants bilaterally, tailoring deals to individual contexts. Deeper information‑sharing and coordinated responses between the Philippines and Vietnam could blunt that approach by making it harder for China to isolate each claimant ⁵

Still, experts caution that the partnership is early stage and limited in its immediate operational bite. The two (2) countries have different strategic rhythms. Manila under Marcos has increasingly practiced what analysts call “assertive transparency”, publicly documenting and highlighting Chinese grey‑zone tactics to raise reputational costs and rally international support. Vietnam, by contrast, balances a posture of persistent resistance with tight diplomatic management and an official policy of “Four No” — no military alliances, no siding with one power against another, no foreign military bases, and no use or threat of force.

Those divergent approaches help explain why the new coast guard link will likely concentrate on confidence‑building measures and non‑traditional security cooperation, search and rescue, incident hotlines, and rules of engagement to reduce miscalculations, rather than joint naval operations or combined enforcement at sea. Joint coastguard drills between Manila and Hanoi only began in 2024, and experts note interoperability, command differences, and bureaucratic hurdles will take time to resolve.

Domestic politics and capacity building also shape the pace of collaboration. Philippine and Vietnamese officials face different institutional structures, logistical priorities and public expectations about how aggressively to confront Chinese actions. “Their political will, based on trust and patience, can serve as a formula to incrementally overcome differences,” said international relations scholars working on the Philippines and Southeast Asia.

The symbolic effect matters. Together, the Philippines and Vietnam are among the most visible ASEAN members willing to push back at sea. Their improved coordination chips away at Beijing’s longstanding advantage of negotiating with each claimant individually. It also signals to outside partners the possibility of more coordinated regional pressure, an outcome that has prompted attention in capitals across the region and beyond. ³ ⁴

China’s coast guard and maritime law enforcement capacity remain significantly larger and better resourced than the combined fleets of the Philippines and Vietnam, a gap that leaves the balance at sea still tilted toward Beijing. And overlapping claims among Southeast Asian states, plus differing economic ties with China, complicate any effort to build a broader, binding maritime coalition within ASEAN.

Even so, the Manila‑Hanoi steps are practical and incremental -- a hotline, maritime incident management mechanisms and expanded information sharing. Those measures, while not a substitute for deeper military cooperation, reduce the risk of accidents and create channels for de‑escalation. They also create templates, rules, standard operating procedures and communication practices, that could be scaled up if political will and capability converge over time. ³

The partnership’s near‑term effect may therefore be political rather than kinetic. It weakens Beijing’s one‑by‑one approach by showing two (2) claimant states can coordinate publicly and diplomatically. Over the longer term, if Manila and Hanoi deepen joint patrols, share sensitive intelligence, or harmonize law‑enforcement responses, the strategic calculus in the West Philippine Sea could shift more dramatically. Analysts caution that such a turning point would require sustained investment in training, interoperable procedures, and a willingness to accept operational risks.

For now, the Philippines is also leveraging relationships with external partners to strengthen deterrent and surveillance capacity. Recent Balikatan exercises and expanded cooperation with allies such as the United States, Japan and Australia, including talks to acquire decommissioned Japanese Abukuma‑class destroyer escorts and Australian surveillance drones, show Manila is combining regional partnerships with bilateral ties to modernize its maritime posture. ³

As Beijing watches how Manila and Hanoi convert diplomatic goodwill into practical tools, the significance of their upgraded ties will hinge on follow‑through. A hotline and coordinated coastguard routines are important risk‑reduction steps; they are not, yet, a blockade of Chinese law enforcement at sea. But they do signal a political convergence, two (2) Southeast Asian claimants strengthening ties and, in doing so, nudging at the limits of China’s preferred method of dealing with its smaller neighbors. ⁵

If the past decade is any guide, change in the West Philippine Sea is likely to be incremental and contested. Manila and Hanoi’s deepening cooperation, cautious, practical and publicly visible, may not instantly overturn the balance at sea. It does, however, raise costs for unilateral moves and creates the scaffolding for more effective regional coordination in the years ahead.

Limits remain

The new ties are still at an early stage, and experts caution that interoperability, command differences, and bureaucracy will take time to work through. Reuters and regional analysis have also noted that China’s maritime enforcement capacity remains far larger than the Philippines’ and Vietnam’s combined resources.

Even so, the political effect is clear. When two (2) of ASEAN’s most visible maritime claimants coordinate more closely, Beijing’s preferred bilaterally focused approach becomes harder to sustain. That does not erase China’s power at sea, but it does narrow the room for pressure tactics.

Why it matters for Manila

For Manila, the point is not to build an anti-China bloc, but to strengthen deterrence, reduce risk, and raise the cost of coercion in the West Philippine Sea. The partnership with Hanoi also fits into the Philippines’ wider effort to deepen defense and surveillance ties with allies such as the United States, Japan, and Australia.

The result is a quiet but important shift -- not a dramatic break in the balance of power, but a steady broadening of Manila’s maritime network. In a contested sea, that kind of incremental change can matter. ²

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Notes:

¹ GMA News. Philippines, Vietnam seal deals on South China Sea security, rice. https://www.gmanetwork.com/news/topstories/nation/895817/philippines-vietnam-seal-deals-on-south-china-sea-security-rice/story

² Philippine News Agency. South China Sea peace a 'non-negotiable' - PH, Vietnam. https://www.pna.gov.ph/articles/1276230.

³ Reuters. Philippines, Vietnam upgrade ties, say South China Sea peace 'non-negotiable'. https://www.reuters.com/world/asia-pacific/philippines-vietnam-elevate-ties-enhanced-strategic-partnership-2026-06-01

⁴ Manila Bulletin. Philippines, Vietnam reaffirm support for 2016 South China Sea arbitral ruling. https://mb.com.ph/2026/06/01/philippines-vietnam-reaffirm-support-for-2016-south-china-sea-arbitral-ruling

⁵ ABS-CBN News. PH, Vietnam elevate defense ties with fresh deals to jointly address South China Sea issues. https://www.abs-cbn.com/news/nation/2026/6/1/marcos-vietnamese-president-to-lam-deepen-bilateral-ties-in-malca-ang-0923