Testing “On An Equal Basis” Or a Three-Way Arms Control Agreement

Key Takeaways

• CTBTO says seismic events were below detectable nuclear‑test levels
• U.S. may cite claim to resume low‑yield testing for modernization
• China’s alleged decoupling would still likely be detectable by IMS
• Three‑way arms‑control talks could become a diplomatic lever

Pulse Analysis

The recent statement by U.S. Under Secretary Thomas DiNanno revives a contentious debate over nuclear‑test verification. While DiNanno alleges that China performed a yield‑producing experiment in 2020, the Comprehensive Nuclear‑Test‑Ban Treaty Organization (CTBTO) counters that the seismic signatures recorded were far too weak to indicate a nuclear explosion. This clash underscores the technical challenges of distinguishing genuine tests from low‑yield or decoupled events, especially when the International Monitoring System can reliably detect explosions as small as 10‑50 tons of TNT equivalent. The disagreement also reflects broader political maneuvering, as Washington seeks leverage to justify its own testing agenda and to pressure Beijing into a multilateral arms‑control framework.

Beyond the immediate claim, the episode exposes structural weaknesses in the CTBT regime. Both the United States and China have signed but not ratified the treaty, meaning they are bound by the treaty’s “object and purpose” clause but lack the legal authority to request on‑site inspections. Without ratification, the CTBTO’s verification tools remain largely observational, limiting the ability to enforce compliance. For the U.S., ratifying the treaty would unlock inspection rights and strengthen its diplomatic position, while China’s ratification could create a reciprocal mechanism to address mutual suspicions. The current stalemate therefore fuels a strategic calculus where each side may resort to low‑yield or subcritical experiments to advance weapons modernization while staying under the detection radar.

The broader strategic implication is the potential reshaping of nuclear arms control in a post‑New START era. As the United States contemplates resuming underground tests—potentially on an "equal basis" with China and Russia—the prospect of a three‑way arms‑control agreement gains urgency. Such a pact could introduce new limits, verification protocols, and confidence‑building measures, mitigating the risk of an unchecked arms race. However, achieving consensus will require both superpowers to overcome domestic political resistance to treaty ratification and to align on acceptable yield thresholds. The outcome will significantly influence global non‑proliferation efforts and the future stability of the nuclear balance of power.