On May 26, the foreign ministers of the United States, Japan, India, and Australia convened in New Delhi for the Quadrilateral Security Dialogue (Quad) and issued a joint statement. The document reaffirms the group's longstanding "free and open Indo-Pacific" framework and introduces concrete initiatives across four pillars—maritime and transnational security, economic prosperity and security, critical and emerging technologies, and humanitarian assistance and disaster response. Notable measures include advancing the operationalization of the Indo-Pacific Maritime Domain Awareness program in the Indian Ocean region, launching the Indo-Pacific Maritime Surveillance Collaboration, and moving toward the normalization of Quad maritime ship observation missions. The statement also devotes significant attention to the South China Sea, cataloguing alleged "dangerous and coercive actions" and referencing the 2016 arbitral award. These developments indicate that the Quad intends to incorporate the South China Sea issue more systematically into its agenda through enhanced maritime domain awareness, diplomatic narrative-building, and efforts to shape regional rules and order. The trajectory and potential risks merit close attention.

The Quad's engagement with the South China Sea is most clearly reflected in the institutionalization and systematization of its maritime security capabilities. The newly announced IPMDA and IPMSC initiatives are designed to enable real-time intelligence sharing and the development of a common operational picture among the four countries. Over recent years, successive Quad statements have repeatedly highlighted the South China Sea, steadily expanding intelligence exchanges, joint exercises, and surveillance coordination. The goal is to achieve comprehensive monitoring of navigation, resource development, and law enforcement activities across key "Indo-Pacific" waters. While these efforts are presented under the banner of "freedom of navigation" and "maritime security", they substantially increase the capacity of external actors to track and potentially interfere with China's routine sovereign activities in waters under its jurisdiction. This directly affects China's maritime rights and security interests.

On the diplomatic and narrative front, the Quad has consistently used joint statements and high-level meetings to coordinate messaging and establish a relatively fixed pattern of negative framing. The 2026 statement's criticisms of China follow the same template as previous outputs. It largely disregards the historical context of the South China Sea issue and seeks to cultivate an external perception that China is destabilizing the region, while endorsing the 2016 arbitral award. In doing so, the Quad is attempting to shift the South China Sea question away from the established track of direct bilateral consultations and negotiations among the parties concerned. This approach risks complicating relations between China and other claimants and places pressure on the "dual-track" approach—pursuing bilateral dispute resolution alongside China–ASEAN cooperation—that China has long advocated and that has received support from ASEAN members. In reality, China and ASEAN countries have for years upheld the principle that disputes should be resolved peacefully through direct negotiations between the parties involved, and that peace and stability in the South China Sea should be jointly maintained by China and ASEAN. This shared commitment is the primary reason the situation in the South China Sea has remained generally stable.

The Quad's continued intensification of activities could trigger a series of secondary effects that disturb the broader regional peace and stability. Heightened maritime surveillance of China may prompt corresponding adjustments in regional force deployments, raising the risk of unintended air and maritime incidents or sudden confrontations. If supply-chain "de-risking" measures extend further into South China Sea shipping lanes or marine resource sectors, they could disrupt normal regional trade and marine economic cooperation. Repeated negative narratives may also entrench misconceptions in the international community, hindering rational dialogue grounded in objective facts and international law.

At a deeper level, the Quad's growing momentum reflects the interplay between the long-term strategic calculations and structural anxieties of its members, particularly the United States and Japan, which further complicates the South China Sea issue. First, US policy on maritime matters and its broader China strategy exhibits strong continuity. From the "Asia-Pacific rebalance" to the "Indo-Pacific strategy", successive US administrations—despite differences in style—have treated maritime security as a central lever in strategic competition with China and relied on alliances and partnerships to constrain Beijing. The current push to normalize Quad maritime surveillance and institutionalize intelligence sharing represents a logical extension of this approach, reframing unilateral US involvement as multilateral collective action to sustain a more enduring presence in the South China Sea. Second, Japan's motivation to use the Quad as a platform to constrain China and loosen postwar constitutional constraints on its own military has become increasingly pronounced. Tokyo views the mechanism as a vehicle for advancing its "normal country" agenda.

By amplifying concerns over a "China threat", Japan has actively supported the normalization of ship observation missions extending toward the southwestern islands, while accelerating revisions to its national security documents, increasing defense budgets, and developing counter-strike capabilities—moves that elevate regional military risk. Third, US allies and partners are showing heightened anxiety about the reliability of long-term American security commitments. Japan and Australia, among others, harbor doubts about Washington's future policy consistency, while India remains cautious about potential US shifts. In response, these countries are both working harder to anchor the United States in the "Indo-Pacific" through minilateral mechanisms and accelerating their own defense modernization and intra-alliance cooperation. This dual logic of "binding the US" and "self-strengthening for hedging" has paradoxically accelerated the Quad's institutionalization and drawn the South China Sea deeper into great-power rivalry.

It is evident that the Quad's strategic posture ultimately serves the objectives of the US' "Indo-Pacific" strategy. The mechanism functions as a tool for Washington to construct exclusive minilateral groupings, advance geopolitical competition, and preserve its maritime primacy. By integrating cooperation across maritime security, supply-chain resilience, and emerging technology standards, the Quad has built a multi-layered, all-domain network. Although framed as promoting "diversification" and regional "resilience", its real aim is to counter the steady development of China's maritime capabilities and maintain US dominance in the Western Pacific. While the Quad routinely affirms respect for ASEAN centrality, its institutional design and implementation reveal an effort to create a parallel security architecture that could dilute ASEAN's voice and coordinating role in regional affairs.

That said, the Quad's expanded "whole-of-domain" presence, while increasing its visibility and operational reach, faces multiple constraints. The four countries harbor significant differences in strategic priorities, China policies, and core interests, making full operational alignment difficult. The vast majority of ASEAN states continue to prioritize strategic autonomy and decline to be drawn into great-power confrontation, limiting the Quad's regional appeal and legitimacy. Most importantly, the fundamental stability of the South China Sea remains resilient because China itself is a steadfast guardian of regional peace and a cornerstone of stability. China consistently advocates the peaceful resolution of disputes through friendly consultations with the parties directly concerned. It works with ASEAN to fully and effectively implement the Declaration on the Conduct of Parties in the South China Sea, accelerates consultations on a Code of Conduct, promotes practical maritime cooperation, and refines crisis-management mechanisms. These efforts have effectively preserved peace, stability, and freedom of navigation in the South China Sea.

The shared desire of regional countries for peace and development, combined with China's firm commitment and concrete actions to uphold stability, forms a solid barrier against external interference. Consequently, although the Quad's influence on the regional situation is expanding, it cannot fundamentally alter the underlying stability of the South China Sea.

The author is the director of the Center for International and Regional Studies, National Institute for South China Sea Studies.

The views don't necessarily reflect those of China Daily.

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