A schism is clear in ASEAN’s approach to the South China Sea. Bound by the stipulated deadline of 2026 for its South China Sea’s Code of Conduct (CoC) negotiations, the institution has struggled to bridge varying member states’ claims, interests, and preferences for dealing with China. These differences were so intractable that ASEAN failed to even produce a statement for the 2016 ruling on the South China Sea. A decade on as ASEAN approaches the 2026 countdown, the rift between mainland and maritime states appears equally as deep. Cambodia, Thailand, and Laos are poised to be buffeted by economic headwinds stemming from US trade policy, potentially pushing them closer to China’s economic orbit and frustrating ASEAN progress on the CoC. On the other hand, maritime states like the Philippines grow louder and more visible in their complaints against sovereignty intrusions by the Chinese military. The polarization between mainland and maritime states is clear to all observers – a majority of participants at the Dialogue on Maritime Security believed that the CoC would never be completed, casting a pessimistic shadow on ASEAN’s legitimacy. 

Yet, this mainland-maritime split may not be as intractable as it appears. There are common interests in gathering regional buy-in and support for parallel territorial conflicts with China, namely the Mekong Delta for mainland states and the South China Sea for maritime states. Both conflicts involve China’s encroachment on the sovereignty of Southeast Asian states, either through controlling upstream river flows or building military installations in claimants’ territorial waters. Even the resistance from other ASEAN member states to taking a stronger, collective stand is driven by remarkably similar concerns – that the risk of imperiling economic ties with China outweighs the benefits of using regional mechanisms to address China’s behavior. In fact, China is also aware of these similarities, with Chinese academics warning that the “Mekong must not become (the) second South China Sea”. Yet, precisely through drawing the parallels between these two conflicts can maritime states incentivize mainland ones to be more involved in the South China Sea, and vice versa. Any breakthrough in one conflict acts as a model for engagement in the other, and ASEAN’s region-wide commitment to safeguarding territorial sovereignty holds water across two conflicts. 

The conditions for intertwining these conflicts are apt. Mainland states have been working to build support for the Mekong issue, and they should be backed by maritime states, who desire a similar response in the South China Sea. Vietnam, which straddles both conflicts, has been trying to incorporate the Mekong Delta issue into ASEAN’s overall agenda, unfortunately to little success. Thailand, with its longstanding silence on the South China Sea, has been developing the Ayeyarwady-Chao Phraya-Mekong Economic Cooperation Strategy as a caucus between the five mainland countries and a counterbalance to China’s Lancang-Mekong mechanism. Even Cambodia, which has been harshly termed a client state of China, has been quietly diversifying its economic and defense partners since Hun Manet’s rise to power, providing a timely opportunity for ASEAN to seek Cambodia’s silence as member states push to conclude CoC negotiations.

With the Philippines poised to take the ASEAN Chair next year, President Marcos has stated his desire to finalize a legally binding CoC before the 2026 deadline. In the remaining 18 months, however, Manila may find more progress in taking a step back and engaging with mainland states on the Mekong Delta issue as well as creating incentives for a similar response in the South China Sea. 

The views contained in this article are the author’s own. The content herein does not necessarily represent the views of Expeditors and its affiliates, divisions, subsidiaries, officers, directors, and employees.

Olivia is a senior analyst in Onyx’s Asia Practice and leads the firm’s work on China, in addition to other regional and industry-level analysis. She is also a Pacific Forum Young Leader, where she focuses on Southeast Asian security issues. She holds honors degrees in History and International Political Economy from the National University of Singapore and Nanyang Technological University. Her work has been featured in the Pacific Forum, The Asia Times, The Diplomat, The China Project and other media outlets.

Photo: The sun sets over the Mekong River in Vietnam. Credit: Shutterstock file photo.