Negative Security Assurance

A negative security assurance (NSA) is a commitment by one of the recognised nuclear-weapon states — the United States, Russia, United Kingdom, France, and China — that it will not use or threaten to use nuclear weapons against states that do not possess them. NSAs are politically central to the bargain underlying the Treaty on the Non-Proliferation of Nuclear Weapons (NPT): non-nuclear-weapon states forgo acquiring nuclear arms partly in exchange for protection from nuclear coercion.

Each of the five NPT nuclear-weapon states has issued its own unilateral NSA declaration, and the wording differs significantly. China's pledge is the most unconditional, stating it will never use or threaten nuclear weapons against non-nuclear-weapon states or nuclear-weapon-free zones. The United States, United Kingdom, France, and Russia have historically attached caveats — for example, exempting non-nuclear-weapon states acting "in association" with a nuclear-armed state in an attack, or reserving the right to respond to chemical or biological attacks. The U.S. 2010 and 2022 Nuclear Posture Reviews narrowed but did not remove such conditions.

These unilateral pledges were collectively noted by the UN Security Council in Resolution 984 (1995), adopted just before the NPT Review and Extension Conference, which also recognised so-called positive security assurances (commitments to seek Security Council action if a non-nuclear state is attacked with nuclear weapons).

NSAs also appear in legally binding form through protocols to nuclear-weapon-free-zone treaties — for instance the Treaty of Tlatelolco (Latin America, 1967), the Treaty of Rarotonga (South Pacific, 1985), the Treaty of Pelindaba (Africa, 1996), the Bangkok Treaty (Southeast Asia, 1995), and the Treaty of Semipalatinsk (Central Asia, 2006). Non-nuclear-weapon states, particularly through the Non-Aligned Movement and the New Agenda Coalition, have repeatedly called at NPT Review Conferences for a single, universal, legally binding NSA instrument — a demand that has not been met.