Benjamin Netanyahu has said Israel will sign up to an international treaty banning nuclear tests, adding that it is a question of “when, not if”.

The Israeli prime minister’s remarks were relayed by Lassina Zerbo, head of the Comprehensive Test Ban Treaty Organization and a top United Nations diplomat, after a meeting between the two men on Monday.

Israel, an undeclared nuclear weapons state since the 1960s, is one of only eight countries not to have signed up to the 1996 Comprehensive Nuclear Test Ban Treaty (CTBT). In addition, it is one of only three states not to have signed up to the Nuclear Non-Proliferation Treaty (NPT), alongside India and Pakistan.

Zerbo considers Israeli buy-in as essential to a nuclear-free Middle East, but Netanyahu’s office was quick to add conditions, saying that while Israel supports the treaty, ratification “depends on the regional context and the appropriate timing”.

Last year, Israel joined high-level diplomatic NPT meetings as an observer, but it insists that regional security arrangements must precede any talks on disarmament.