China’s Growing Maritime Influence in Southeast Asia

Over the past decade, the South China Sea has develop into a focal point of strategic competition between the United States and China. As geopolitical uncertainties surrounding U.S. Alliances grow, China is increasingly positioning itself as a key partner for Southeast Asian nations, particularly in the realms of the blue economy and maritime security. This shift is driven by China’s substantial investment in the region and its efforts to build a new maritime order, though its success hinges on curbing coercive behavior in the South China Sea and offering a viable alternative to U.S. Engagement.

China’s Investment in the Blue Economy

China is a leading investor in the blue economy of Southeast Asia, with estimated joint investments with the Association of Southeast Asian Nations (ASEAN) ranging from US$2.0 trillion to US$3.7 trillion between 2020 and 2050. USNI News reports that initiatives include establishing green shipping lanes in the Strait of Malacca and supporting eco-friendly coastal aquaculture. These projects align with the interests of many Southeast Asian countries, focusing on balancing economic growth with environmental protection.

Multilateral Efforts and International Positioning

China is actively leading multilateral efforts to shape the maritime environment, having signed and ratified the Biodiversity Beyond National Jurisdiction Treaty and bidding to host its secretariat. The Congressional Research Service highlights this as a symbolic move that contrasts with the United States, which has only signed the treaty and withdrew from 66 international treaties in January 2025.

Tensions in the South China Sea and Shifting Alliances

Despite these economic and diplomatic efforts, the ongoing conflict and tensions in the South China Sea, where China asserts expansive and contested claims, remain a significant challenge. The U.S. State Department condemned China’s actions against a Philippine vessel near Thitu Island in October 2025, underscoring the continued tensions. However, growing uncertainty about the reliability of the U.S. As an ally is prompting some countries in the region to cooperate with China.

Strengthening Ties Between China and Southeast Asian Nations

Indonesia has agreed to a joint development project with China in overlapping claimed areas, despite concerns about its legality. Malaysia and Cambodia conducted military drills with China in 2025. Vietnam and the Philippines have expressed concerns about U.S. Reliability, with reports suggesting Vietnam is planning for scenarios involving diminished U.S. Support. GMANetwork reports that Vietnam conducted its first joint military drill with China last year.

The ‘Maritime Community with a Shared Future’

China first proposed building a ‘Maritime Community with a Shared Future’ in 2019. While initially met with skepticism due to China’s coercive behavior in the South China Sea and the perceived reliability of the U.S., this proposal is gaining traction amid increasing uncertainty about U.S. Commitment to the region.

Factors Determining the Success of a China-Led Maritime Order

The success of a China-led maritime order in Southeast Asia depends on two key factors. First, the availability of alternatives to China for maritime cooperation. Second, China’s behavior in the South China Sea. If China continues aggressive tactics, resistance will persist. However, increased cooperation could lead to broader regional support for its proposed maritime order.

Philippines and US Bolster Defense Cooperation

In February 2026, the Philippines and the United States announced plans to increase deterrence against aggression in the South China Sea, including increased deployments of U.S. Missile and unmanned systems to the Philippines. GMANetwork reported that the U.S. Will also provide $144 million for infrastructure development at Philippine military sites used by American troops under the Enhanced Defense Cooperation Agreement (EDCA).