A Nuclear-Free Southeast Asia and the Significance of China’s Move to Sign the SEANWFZ Protocol

Introduction

Nuclear disarmament initiatives in Southeast Asia constitute a remarkable example not only in terms of the regional security architecture but also regarding the functioning of global disarmament regimes. The Southeast Asia Nuclear Weapon-Free Zone (SEANWFZ), established by the 1995 Bangkok Treaty, imposed obligations on ASEAN member states prohibiting the possession, development, and use of nuclear weapons. However, the full operationalization of the treaty is directly dependent on the five permanent members of the United Nations Security Council signing and ratifying the SEANWFZ Protocol (Nuclear Threat Initiative [NTI], 2024; ASEAN, 2025). The full text of the Protocol is available on the official ASEAN website.

According to a statement made by Malaysian Foreign Minister Mohamad Hasan in July 2025, China has pledged to sign the protocol without reservations once all necessary documents are prepared (Reuters, 2025). Chinese Foreign Ministry Spokesperson Mao Ning also affirmed that China has always supported the establishment of a nuclear-weapon-free zone in Southeast Asia and is ready to take a leading role in signing the protocol (Reuters, 2025).

This study examines China’s approach to the SEANWFZ Protocol within the context of its historical background, nuclear policy, South China Sea claims, and relations with ASEAN, while also considering the positions of other nuclear powers. It argues that China’s decision to sign the protocol is not merely symbolic but a strategic move with potential implications for both regional and global security. By balancing diplomatic signaling through commitment to the “No First Use” doctrine and engagement with ASEAN, with rapid nuclear modernization, China demonstrates a complex strategy that integrates credibility-building, power projection, and deterrence. Understanding this dual approach is essential for assessing how China’s actions may shape regional dynamics and the broader framework of nuclear arms control.

Background: The Emergence and Significance of the SEANWFZ

The SEANWFZ Treaty, also known as the Bangkok Treaty, entered into force on March 28, 1997, and its purpose is to preserve Southeast Asia as a Nuclear-Weapon-Free Zone, an objective that emerged from the aim of being free from weapons of mass destruction. The idea of the Southeast Asia Nuclear Weapon-Free Zone (SEANWFZ) arose with the “Zone of Peace, Freedom and Neutrality” (ZOPFAN) Declaration signed on November 27, 1971, in Kuala Lumpur by the first five members of the Association of Southeast Asian Nations (ASEAN). In this process, due to the negative political environment in the region, the treaty process was suspended in the mid-1980s. As a result of ten years of negotiations, the SEANWFZ Treaty was signed on December 15, 1995, in Bangkok by the heads of government of all ten states in the region: Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam (Nuclear Threat Initiative [NTI], 2024).

Within the scope of the obligations of the treaty, the states parties undertake not to possess, develop, test, or use nuclear weapons. In addition, within these obligations, they refrain from receiving or providing any assistance related to nuclear weapons and do not encourage the production of nuclear explosive devices. Without the safeguards of the IAEA (International Atomic Energy Agency), they cannot supply nuclear material. The treaty prevents the possession and testing of nuclear devices within the region, prohibits the dumping of radioactive waste into the sea, and aims primarily to ensure the protection of coastal waters (Nuclear Threat Initiative [NTI], 2024).

The SEANWFZ Treaty is regarded as an important legal instrument supporting the objectives of ASEAN. The entry into force of this protocol bears great significance in terms of contributing to the preservation of Southeast Asia as a zone of neutrality and peace, within the context of the increasing great power competition in the Asia-Pacific region (Zhao, 2017; United Nations, n.d.).

China’s Traditional Nuclear Policy in the Context of the Prohibition of Nuclear Weapons and Its Approach to the SEANWFZ Protocol: Diplomacy vs. Capability

According to the Ministry of Foreign Affairs of the People’s Republic of China (2024), China regards the non-use and eventual elimination of nuclear weapons as a fundamental goal for international security, while emphasizing that it develops its own nuclear weapons solely for defensive purposes and encourages other nuclear-weapon states to adopt a mutual ‘no first use’ commitment. This approach enhances international confidence, contributes to reducing global strategic risks, and supports disarmament objectives within the framework of the NPT (Ha, 2023; State Council Information Office of the People’s Republic of China, 2019).

China’s readiness to sign the SEANWFZ Protocol represents a long-standing stance dating back to 1999. Beijing has repeatedly indicated its willingness to sign the Protocol and even suggested that it could be the first Nuclear-Weapon State (NWS) to do so without reservations. Regarding China’s nuclear doctrine, it evolves within the context of the changing external security environment and increasing nuclear capabilities. Throughout this process, China is known to maintain its defensive posture and its unconditional “No First Use” (NFU) policy, as confirmed in China’s 2019 Defense White Paper (Ha, 2023; State Council Information Office of the People’s Republic of China, 2019).

China shapes its policies supporting nuclear disarmament in Asia within the framework of both enhancing regional security and strengthening its global strategic image. The decision to sign the SEANWFZ Protocol is seen as a diplomatic message supporting regional security while reaffirming the NFU principle. This step is part of China’s broader diplomatic strategy to strengthen relations with ASEAN countries and support regional stability. The signing of the protocol concretizes China’s rhetoric of limiting nuclear weapons use, while also paralleling its territorial claims in the South China Sea and its strategy to maintain a military presence in the region (Indo-Pacific Defense Forum, 2025).

China’s participation in the SEANWFZ Protocol is not limited to nuclear disarmament and regional security goals; it is also linked to a strategy of shaping regional power balances in its favor. This situation reveals the complex interaction between China’s diplomatic rhetoric and strategic interests, creating both opportunities and uncertainties in terms of regional security architecture and nuclear weapons control efforts (Ha, 2023; Ngân, 2025; NTI, 2024; Reuters, 2025). China’s strategic calculations in Asia aim to reduce risks from regional instabilities and strengthen its diplomatic image as a “peaceful leader” (Indo-Pacific Defense Forum, 2025).

China’s acceptance in July 2025 to sign the SEANWFZ Agreement reflects this strategy. Signed by ASEAN members in 1995 and enforced in 1997, the agreement prohibits member countries from possessing or using nuclear weapons on their territories, in exclusive economic zones, or on continental shelves. China’s move not only serves the purpose of preventing nuclear proliferation but also has the potential to increase its influence in the region and affect cooperation between the U.S. and its allies. Its implementation could alter the security balances of countries relying on the U.S. “nuclear umbrella” policy, such as the Philippines, Singapore, and Thailand. However, the SEANWFZ agreement does not limit China’s existing nuclear arsenal; its benefits are primarily political and strategic, portraying China as a responsible nuclear actor (Indo-Pacific Defense Forum, 2025).

China’s growing nuclear arsenal demonstrates the gap between its diplomatic rhetoric and strategic realities. According to SIPRI data, China’s nuclear warheads increased from approximately 410 in 2023 to over 600 in 2025. Around 350 new intercontinental ballistic missile (ICBM) silos constructed in the northern and eastern regions have significantly enhanced China’s deterrence capability. This rapid growth has major implications for regional and global strategic balances. The expansion of China’s nuclear arsenal at this scale influences the strategic perceptions of actors such as India, Japan, and the U.S., potentially triggering an arms race (Indo-Pacific Defense Forum, 2025).

In a global context, as shown in the following table, China’s nuclear arsenal of 600 warheads remains smaller than that of the U.S. and Russia, yet its modernization and expansion of delivery systems enhance its regional influence and strategic weight. This demonstrates how China’s dual-track approach—projecting itself diplomatically as a supporter of disarmament while expanding its military capacity—is designed to consolidate strategic leadership, strengthen deterrence, and secure regional interests (SIPRI Yearbook, 2025; SCMP, 2023).

Source: SIPRI, 2025

China’s support for nuclear disarmament in Asia can be understood as a combination of efforts to reduce regional security risks, maintain stability, and reinforce its diplomatic relations with ASEAN countries. This approach reflects China’s attempt to balance its role as a regional actor with its strategic interests, projecting a commitment to disarmament while simultaneously ensuring the security of its national and regional objectives (SIPRI, 2025).

Reasons Why China Did Not Sign the Agreement Earlier

Even though the SEANWFZ Treaty was signed nearly 30 years ago, none of the five recognized NWS states have yet definitively become a party to the protocol. When looking at these five NWS, they face problems largely due to issues considered significant, such as the ambiguous and broad geographical scope, the comprehensive nuclear security assurances envisaged in the Protocol, and the matters concerning port visits and transits of foreign ships and aircraft in the region. For these reasons, they generally experience problems and face security concerns (Ha, 2023).

However, among these five NWS, apart from four of them, China is known to have rarely taken a clear position regarding these issues. So far, the only concern expressed by China with respect to SEANWFZ is that the Treaty and the Protocol may conflict with or undermine its territorial and maritime rights and interests in the South China Sea (SCS) (Ha, 2023).

When looking at China’s concerns in more detail, they are related to the possibility that signing the treaty could affect territorial claims in the South China Sea involving Malaysia, Brunei, and the Philippines. In addition, the strong support of Vietnam for the treaty, as a country that has experienced military conflict with China in the past, is known to have increased China’s concern that its military options in Southeast Asia could be restricted. China has perceived this process as ASEAN’s attempt to limit the use of force in the South China Sea. China has conveyed these concerns to ASEAN in the past and stated that it would not sign the protocol unless convinced (Kaur, 2022).

In addition to this concern, during the negotiations between 2010 and 2012, it is known that the SEANWFZ state parties and China agreed to sign a Memorandum of Understanding (MoU) stating that the Treaty and the Protocol would not affect their land territories, EEZs, and CSs (Kaur, 2022).

China’s Claims and Concept of Sovereignty in the South China Sea

In the event that all NWS join the SEANWFZ Protocol, they would be bound by the same legal obligations; however, the strategic security implications differ significantly for the P4 and China, since only China is located within the region. China makes excessive sovereignty and maritime jurisdiction claims within the framework of the Nine-Dash Line, which covers about 90% of the South China Sea (SCS); moreover, it further expands these claims through the “Four Sha” concept. This approach encompasses all maritime areas, including internal waters, territorial seas, contiguous zones, exclusive economic zones (EEZ), and continental shelves (CS), based on the four outlying archipelagos in the SCS (the Pratas, Paracels, Spratlys, and Macclesfield Bank). However, as a continental state, China is prohibited under UNCLOS from making such claims. In addition, China has demanded the signing of a Memorandum of Understanding (MoU) in order to ensure that SEANWFZ does not interfere with its sovereignty and maritime rights. This situation effectively guarantees Beijing’s selective and flexible interpretation of SEANWFZ’s geographical scope in line with its own interests. Indeed, China may regard the deployments of other nuclear-armed states in the region as violations of SEANWFZ; by contrast, it could legitimize the presence of its own nuclear assets on the grounds that such deployments take place within China’s (claimed) sovereignty and jurisdiction (Ha, 2023).

China-ASEAN Relations in the Context of SEANWFZ

From a strategic perspective, the SEANWFZ treaty carries strong symbolic significance. In this symbolic sense, it has been highlighted as a stance that reinforces ASEAN’s determination to remain distant from global power competition, as well as its mediating role in preserving the international order. China’s potential participation in the SEANWFZ is seen as a diplomatic gain for ASEAN, while also carrying unpredictable risks (Ngân, 2025).

China’s intention to sign the SEANWFZ Treaty can be regarded as a diplomatic development for ASEAN, and it is also expected to strengthen the legal validity of the treaty. However, China’s participation entails certain risks due to its potential to introduce differing interpretations on issues such as territorial scope and disputed areas in the South China Sea. In addition, the signing of the treaty may affect intra-bloc dynamics and could shape the responses of some member states. In this context, ASEAN’s support for the implementation of the treaty through transparent and verifiable mechanisms is important for limiting strategic uncertainties and enhancing the effectiveness of the initiative (Ngân, 2025).

Approaches of Other Nuclear Powers to the Treaty

The SEANWFZ Protocol, as an important element of regional nuclear disarmament efforts, is evaluated within the framework of the positions of other Nuclear-Weapon States (NWS), primarily the United States and Russia, as well as France and the United Kingdom, and regional security balances (Ha, 2023).

“Package Deal” Issue: SEANWFZ State Parties have long advocated that disputes with all other NWS (the United States, Russia, France, and the United Kingdom) should be resolved collectively and that all of them should accede to the Protocol simultaneously. Therefore, even if some states appear willing, the lack of approval from others is known to hinder the progress of the process (Ha, 2023).

Negative Positions of the United States and Russia: The U.S. withdrawal from the INF Treaty and Russia’s suspension of participation in the New START Treaty demonstrate that NWS are moving away from arms control obligations. The U.S. withdrawal from the INF Treaty raises concerns that it could deploy short-range nuclear missiles in Asia, while Russia’s nuclear coercion in Ukraine has been emphasized as increasing insecurity among non-nuclear states (Ha, 2023).

Strategic Balances: The tension between the U.S. and Russia among NWS is reshaping security balances in the region. In this context, SEANWFZ countries are known to be caught between their “nuclear-weapon-free” objectives and the requirements of “regional power balance. (Ha, 2023)”

Conclusion

This study demonstrates that China’s decision to sign the SEANWFZ Protocol goes beyond a symbolic step toward nuclear disarmament in Southeast Asia; it represents a strategic effort to shape regional security and enhance diplomatic credibility. In alignment with its “No First Use” doctrine, China signals responsible nuclear behavior while strengthening its relations with ASEAN countries.

However, China’s rapid expansion and modernization of its nuclear arsenal reflects a calculated dual-track strategy, simultaneously supporting diplomatic disarmament commitments and maintaining robust deterrence capabilities. This approach addresses regional security concerns, particularly in the South China Sea, while consolidating China’s position amid competition with major powers such as the United States, India, and Japan. At the same time, it seeks to reduce regional instability and reinforce China’s image as a “peaceful leader.”

China’s earlier reluctance to sign the SEANWFZ Protocol can be understood in light of historical concerns, including territorial claims, potential restrictions on military options, and the need for assurances that the Protocol would not infringe upon its sovereignty. By ultimately committing to sign, China balances these security concerns with diplomatic incentives, maintaining strategic flexibility while presenting itself as a responsible actor.

If the Protocol is fully implemented with effective verification mechanisms, Southeast Asia could strengthen its status as a “zone of peace, neutrality, and cooperation.” Nonetheless, China’s increasing nuclear capabilities, coupled with the reservations of other nuclear powers, mean that regional strategic uncertainties will persist. Overall, China’s move represents a calculated initiative that supports regional disarmament while simultaneously consolidating its security, leadership, and deterrence objectives (Indo-Pacific Defense Forum, 2025; SIPRI, 2025; SCMP, 2023; ASEAN, 2025).

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