Why ASEAN Can’t Secure the South China Sea Alone

Balancing regional autonomy with external deterrence is key to managing rising tensions.

When Philippine vessels face daily harassment in the South China Sea, neither unilateral naval deployments nor ASEAN-led cooperation alone can safeguard regional autonomy.

Southeast Asian claimant states face complex strategic realities that cannot be reduced to a simple choice.

A stable and credible security arrangement requires a layered approach that blends bilateral commitments, minilateral cooperation, and ASEAN mechanisms, rather than elevating one avenue at the expense of the others.
The Credible Commitment Challenge

Arguments for scaling back visible naval deployments in favor of capacity building assume claimant states can secure their interests solely through improved capabilities.

This view overlooks a basic reality: without visible and sustained commitment, deterrence weakens.

When external partners limit their engagement to consensus-driven multilateral platforms, they signal deference to the preferences of the most influential regional actor — in this case, China.

The Philippines’ experiences across administrations illustrate this dynamic.

Under Rodrigo Duterte (2016–2022), Manila’s pivot toward Beijing coincided with increased Chinese maritime militia activity near Thitu Island and continued development of disputed facilities.

By contrast, the Marcos administration’s renewed focus on the US–Philippines alliance (2022–2023), including the expansion of military sites where US forces can operate, was followed by noticeably more restrained behavior from the Chinese coast guard.

The 2012 Scarborough Shoal standoff shows the costs of ambiguous engagement: Washington’s lack of a defined posture signaled that seizing control carried limited costs.

In contrast, when a Chinese vessel rammed and sank a Philippine fishing boat at Reed Bank in 2019, the United States swiftly reaffirmed its Mutual Defense Treaty commitments, which effectively curtailed further escalation.

The Consensus Trap and Differentiated Threats

Steady, transparent external engagement helps set behavioral expectations and reduces the risk of miscalculation.

Routine, professional freedom of navigation operations strengthen norms rather than provoke escalation.

Sporadic or ambiguous involvement, however, creates uncertainty and invites probing actions.

ASEAN is often portrayed as a single, cohesive security actor, but member states face different threats.

The Philippines and Vietnam confront direct territorial disputes and frequent harassment of their fishermen, while Malaysia experiences incursions into its exclusive economic zone off Sarawak.

Cambodia and Laos, as major beneficiaries of Chinese investment and political support, repeatedly block efforts to address these tensions.

China consistently resists constraints on its South China Sea ambitions, whether through ASEAN mechanisms, bilateral partnerships, or international arbitration.

The core question is not whether external engagement provokes Chinese criticism — it inevitably does — but whether it provides sufficient deterrence to prevent unilateral actions that alter the status quo.
Interconnected Regional Security and Extended Deterrence

Security in the South China Sea cannot be separated from the broader East Asian balance of power.

Japan’s increasing involvement reflects this reality.

The Taiwan Strait and South China Sea are linked geographically and strategically; any Taiwan contingency would immediately affect Southeast Asian claimant states through blockades, disrupted shipping, and potential combat operations in adjacent waters.

Japan’s 2023 transfer of coastal surveillance radar to the Philippines, alongside ongoing capacity-building programs with Vietnam, demonstrates the tangible value of external support for maritime domain awareness.

ASEAN states neither possess the standalone capabilities to monitor their maritime spaces adequately nor the means to balance China’s power on their own.

Without credible external backing, more ASEAN states may align with Beijing out of necessity rather than choice — a phenomenon scholars call “defensive bandwagoning.” Cambodia’s consistent alignment with Chinese positions exemplifies this calculation, as Chinese economic and political support outweighs the benefits of opposing Beijing.

2026 Philippines’ Chairmanship

As the Philippines prepares to chair ASEAN, it will be essential to recognize the complementary functions of multiple frameworks.

ASEAN provides vital diplomatic architecture and norm-setting, including the ongoing Code of Conduct negotiations. But ASEAN mechanisms alone cannot address the immediate security needs of claimant states or provide deterrence against coercion.

Bilateral alliances, minilateral arrangements, and routine naval presence by external partners serve distinct but necessary roles in maintaining regional stability.

The challenge for policymakers is to ensure these layers reinforce one another. External engagement should enhance — not substitute for — regional capacity and agency. Respecting regional agency means supporting the specific security needs of individual states, not constraining engagement to the pace of consensus decision-making.

The future of the South China Sea will not be decided solely by foreign powers, nor will ASEAN states act alone.

What matters is whether these approaches can be coordinated in time to preserve sovereignty, maritime rights, and freedom from coercion.

Without coordination, the region risks losing its ability to shape outcomes before the balance of power shifts irreversibly.