Nuclear, explained.
A test of a Minuteman III intercontinental ballistic missile at Vandenberg Air Force Base, California (DVIDS)
Nuclear states have every reason to make a negative security assurance legally binding, yet none will act.
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The nuclear pledge that costs nothing – but would mean everything in law The nuclear pledge that costs nothing – but would mean everything in law
A “negative security assurance” is a pledge (Opens in new window) by a nuclear-armed state not to use or threaten to use nuclear weapons against a state that has none. Its counterpart, the positive security assurance (Opens in new window), commits nuclear states to come to the aid of a non-nuclear state if it faces a nuclear threat from elsewhere.
Both are political declarations, not treaty obligations, which is precisely the problem.
With both Iran and Ukraine facing a nuclear-armed power, that is exactly the scenario NSAs exist to guard against – and where a political promise is least likely to hold.
Ask a diplomat working on disarmament in Geneva whether the five nuclear-armed states will ever develop consensus on legally binding negative security assurances and the honest answer is no, not given how these states currently operate. That answer has held for decades in Conference on Disarmament sessions, including this year.
Negative security assurances (NSA) are the least demanding, most achievable item on the entire disarmament agenda, yet the states best placed to grant them keep choosing not to. The promise of a fair and balanced non-proliferation order can be fulfilled with legally binding NSAs. The states must move from political good will towards a legal obligation.
The United States, France and the United Kingdom support unilateral declarations so that they can revise whenever doctrine shifts. China, Pakistan and a handful of other countries take the opposite position, pushing consistently for a legally binding assurance.
The Russia–Ukraine war has normalised nuclear rhetoric that was once considered a serious escalation in itself. The United States and Iran conflict showed how fast a regional dispute can climb toward a dangerous threshold, with claims (Opens in new window) highlighting the US is considering potential use of nuclear weapons against Iran. While US President Donald Trump scoffed at the idea (Opens in new window) when questioned about the prospect last week, the trust deficit between nuclear haves and have nots has grown in recent conflicts. Arms control agreements that once bounded strategic competition between the United States and Russia have expired (Opens in new window), and military doctrines are leaning harder on deterrence and further from restraint.
With both Iran and Ukraine facing a nuclear-armed power, that is exactly the scenario NSAs exist to guard against – and exactly where a political promise is least likely to hold.
This is not an abstract worry confined to Geneva. In South Korea, public support for an independent nuclear arsenal has sat close to 70% (Opens in new window) for years. Japan (Opens in new window) and Germany are also shifting their thinking about keeping the option open through what analysts call nuclear latency, in case the extended-deterrence guarantee looks thinner next year than it does presently. Although all these governments are part of the Nuclear Non-proliferation Treaty, and none intend to leave, the drift is real.
UN Secretary General Antonio Guterres at a high-level segment on Conference on Disarmament in Geneva 2025 (Jean Marc Ferré/UN Photo)
The 2026 Conference on Disarmament (Opens in new window) session (Opens in new window) opened in January with member states acknowledging a security environment under real strain, yet it has again produced thematic discussion rather than negotiation on any of the agenda items. In June, NSAs were again debated with no progress made. NSAs return to the agenda every year without resolution, largely because the Conference runs on consensus, and has been held hostage to parallel progress across other subsidiary bodies.
NSAs face no legal, technical, or financial obstacles for negotiations and a majority of the membership supports them. A binding convention would not require a single warhead to move. It would give non-nuclear states a reason to remain non-nuclear, even when governments change. It would make nuclear coercion more costly, at a time when such threats have re-emerged in two ongoing wars. Above all, it would show that the disarmament commitments made by nuclear-weapon states under the NPT are more than promises on paper.
The strategic cost of credible NSAs is low. The security gain, however, could be measurable. They could reassure countries such as South Korea, Japan and Germany that their security does not have to depend entirely on another state’s nuclear umbrella.
Every year the gap between promise and law stays open and the argument for going nuclear gets a little easier to make in each of those capitals.
About the author
Tayyaba Khurshid
Tayyaba Khurshid works as a research officer at the arms control and disarmament desk, Center for International Strategic Studies AJK.
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