China Wants to Join Southeast Asia’s Nuclear-Free Zone. Why Now?

China is ready to rock with the Treaty of Bangkok.

In a rare appearance at the special online summit for the Association of Southeast Asian Nations (ASEAN) on Nov. 22, China’s President Xi Jinping announced that China is prepared to sign the protocol of a 1995 agreement that establishes Southeast Asia as a nuclear-weapon-free zone. Under the agreement, known as the Bangkok Treaty, 10 regional states renounce the right to nuclear weapons in any form within the ASEAN zone. If it joins the treaty, China would agree not to use or threaten the use of nuclear weapons within the zone or against its members. It would make China the first nuclear-weapon state to adhere.

China’s support for the treaty is no surprise. To strengthen its enduring “no-first-use” policy to never initiate nuclear conflict, China routinely has asserted (most recently in a 2019 white paper) that it “is always committed to … not using or threatening to use nuclear weapons against non-nuclear-weapon-states or nuclear-weapon-free zones unconditionally.” For the Bangkok Treaty, ASEAN and China agreed in 2011 to a secret memorandum of understanding that preserves China’s territorial claims in the South China Sea, removing the greatest hurdle to Beijing’s commitment. China was ready to sign the protocol and memorandum in 2012 but deferred once the other eligible “P-5” nuclear-weapon states under the Non-Proliferation Treaty—France, Russia, the United Kingdom and the U.S.—refused to join. Now, Xi wants to legally bind China to the treaty “as early as possible.” But what’s the rush?

Adherence to the Bangkok Treaty would burnish China’s image amid its rapid expansion in nuclear capabilities. This past summer, analysts discovered that China is building hundreds of new missile silos that could double the size of its intercontinental ballistic missile arsenal and move China away from its minimum nuclear deterrence doctrine. China also tested a nuclear-capable hypersonic missile designed to evade U.S missile defense; U.S. Gen. Mark Milley, Chairman of the Joint Chiefs of Staff, called it a “Sputnik moment.” By promoting the Bangkok Treaty, China can help deflect attention away from its nuclear buildup.

A greater factor in China’s calculus is the AUKUS alliance among the U.S., U.K. and Australia. Under the security partnership announced in September, the U.S. and U.K. agreed to equip Australia with a fleet of nuclear-powered submarines to counter China’s influence in the Indo-Pacific. China is furious and wants to even the score. In a phone call with counterparts from Malaysia and Brunei that same month, Chinese Foreign Minister Wang Yi skewered AUKUS as anathema to the Bangkok Treaty. “The United States and Britain chose not to participate in the SEANWFZ [Southeast Asia Nuclear Weapon-Free-Zone] Treaty,” Wang reminded his peers. “Instead, they have transferred military nuclear technology to the region under various pretexts and also provided the region with highly enriched uranium materials, running counter to the efforts made by ASEAN countries to build a nuclear-free zone.”

China will seek to use the Bangkok Treaty to drive a wedge between ASEAN members and the U.S., the leading partner of AUKUS and the greatest opponent of Southeast Asia’s pact among the P-5. The scope of the zone within the treaty covers waters above the continental shelf and the exclusive economic zones of members some 200 miles out to sea, a strategically vital and vast expanse that stretches from the east Indian Ocean to the western Pacific. Under the treaty, the U.S. would be unable to use or threaten to use nuclear weapons against an enemy vessel within the zone. It also would be unable to use a nuclear-armed submarine within the zone to attack a target elsewhere. While the treaty allows for innocent passage, some observers—including the top U.S. diplomat at the mid-1990s Bangkok Treaty negotiations—believe that even the movement of U.S. nuclear-armed submarines through the zone could be a violation, “as there would be no one within a 150-mile radius to determine whether a certain passage is innocent.”

Beyond legalities, China can use the Bangkok Treaty to inflame broader fears of AUKUS in the region—a tactic that could find fertile ground. Both Indonesia and Malaysia have expressed concern that AUKUS might spark a regional arms race. While Indonesia’s director general for the Asia-Pacific region admitted that AUKUS does not violate the Bangkok Treaty, he did think it could set a “dangerous precedent” for nonproliferation norms. China, meanwhile, can appear as a peacemaker. In confirming China’s readiness to sign the Bangkok Treaty, Indonesia’s foreign minister understood Xi’s remarks to emphasize the need to “create a peaceful home, by strengthening dialogue, multilateralism, [and] rejecting power politics” in Southeast Asia. China also seeks to link the threat AUKUS poses to the Bangkok Treaty with a southern counterpart. In his phone call with the foreign ministers of Malaysia and Brunei, Wang warned that AUKUS would likewise turn the 1985 Treaty of Rarotonga for a nuclear-free South Pacific into “a dead letter.”

ASEAN created the Bangkok Treaty in the mid-1990s in large part to contain China. Now, China seeks to join the pact to use it to expand its own influence and constrain the capabilities of the U.S. and its allies. For its part, the U.S. would do well to reach compromises with ASEAN that would allow it to adhere to the zone. As it has with other nuclear-weapon-free zones, the U.S. could sign the treaty with an interpretive declaration that clarifies what it is willing to accept under the agreement. A joint communique between the P-5 last week offers some hope. Under the statement, the U.S. acknowledged “the importance of advancing discussions” with ASEAN on the Bangkok Treaty protocol. A failure to act now will only strengthen China’s use of the Bangkok Treaty as a diplomatic weapon in the future.