Russia’s parliament took the first step on Tuesday towards revoking ratification of the Comprehensive Nuclear Test Ban Treaty and its top lawmaker hinted it might go further by abandoning the pact altogether.

Parliament’s lower house, the Duma, voted by 412 to zero, with no abstentions, to approve the withdrawal of the ratification in the first of three readings.

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.

But arms control experts are concerned that Russia may be inching towards a test that would be perceived as a threatening signal by the West at a time of heightened confrontation over Russia’s war in Ukraine.