Russian President Vladimir Putin on Thursday signed a law revoking Russia’s ratification of the Nuclear Test Ban Treaty (CTBT), against a backdrop of conflict in Ukraine and a crisis with the West.

The document, which was published on the official legal information portal, had been approved by the upper house of the Russian parliament at the end of October.

Russia says the aim is to restore parity with the United States, which has signed but never ratified the 1996 treaty, and that it will not resume testing unless Washington does.