The comprehensive Treaty on the Prohibition of Nuclear Weapons (TPNW) was adopted by 122 countries in New York in 2017, although the nine nuclear powers were not part of that group.
It prohibits nuclear weapon activities including development, testing, production, acquisition, possession and stockpiling, among others.
The treaty was promoted by the Geneva-based organisation International Campaign to Abolish Nuclear Weapons (ICAN) which received a Nobel Peace Prize for its efforts.
Switzerland adopted the treaty last year but asked for clarification on a number of issues. The TPNW will not come into force until at least 50 countries have ratified it.
Now, the Swiss government have said it will not sign the treaty “at this juncture”.
In a statement on Wednesday explaining the decision, the Federal Council said that while it remained committed to nuclear disarmament, “the arguments against joining the TPNW outweighed the potential opportunities of joining” at this time.
Citing the findings of a parliamentary working group, the Swiss government said that “in the current international context, the TPNW entails risks in terms of both the continued advancement of disarmament diplomacy and Switzerland's security policy interests”.
The working group report itself notes that should Switzerland sign up to the TPNW, it would, in extreme cases of self-defence “reduce its freedom of action and abandon the option of explicitly placing itself under a nuclear umbrella within the framework” of self-defence alliances “not least with nuclear weapon states or their allies” – taken by Swiss daily Tages Anzeiger to be a reference to NATO.
Switzerland said it would “closely monitor further developments and remain committed in this matter” and would re-examine its position in the future as necessary.