Russian President Vladimir Putin signed this Thursday the law that revokes the ratification of the Comprehensive Nuclear Test Ban Treaty (CTBT), with the conflict in Ukraine and the crisis with the West as a backdrop. The 1996 treaty bans all nuclear weapons tests, although it never came into force because some key countries – including the United States and China – never ratified it.

Putin said in early October that his country could revoke its ratification of the CTBT in response to the United States never ratifying it. “I’m not ready to say whether or not we should resume testing,” he added, while praising the development of new missiles that can carry nuclear warheads.

The promulgation of the Russian law is “very disappointing and deeply regrettable,” Robert Floyd, executive secretary of the organization responsible for the treaty (OTPCE, CTBTO), reacted in a statement. Floyd pointed out, however, that despite this decision, Russia claimed to “remain associated” with the treaty, “including the operation of all CTBTO surveillance stations on its territory,” which allow the detection of even the slightest burst.

Since the start of the conflict in Ukraine in February 2022, senior Russian officials have threatened to use nuclear weapons on several occasions, although on other occasions Putin has shown caution in this regard. Last week, the Russian president supervised ballistic missile exercises to prepare his troops for a “massive nuclear attack” of retaliation. The bill to revoke the treaty was approved by the Russian Parliament last month.

Although it never came into force, the agreement was ratified by 178 countries, including nuclear powers France and the United Kingdom, and has symbolic value. Proponents say it establishes an international norm against nuclear weapons testing, but critics say the deal’s potential remains unrealized without ratifications by major nuclear powers. The Russian parliament ratified the agreement in June 2000, six months after Putin became president.

By abandoning the treaty banning nuclear tests, Russia is taking “a big step in the wrong direction,” the head of US diplomacy, Antony Blinken, said on Thursday, calling on Moscow not to carry out tests.

“Unfortunately, this constitutes a step in the wrong direction, moving us further, rather than closer, to the entry into force” of this treaty, Blinken continued in a press release. “This continues Moscow’s disturbing and misguided effort to increase nuclear risks and escalate tensions while pursuing its illegal war against Ukraine,” he said.

“Russian officials say Russia’s planned move to withdraw its ratification does not mean it will resume testing, and we urge Moscow to stand by those statements.” Both the United States and China, unlike Russia, have never ratified the treaty, a key obstacle to its entry into force.

President George H.W. Bush enacted a unilateral ban on US nuclear testing in 1992 that has since been extended. But the Senate refused to ratify the test ban treaty in 1999.

President Biden and his Democratic predecessors have supported ratification, but treaties under the U.S. Constitution require two-thirds support, a prohibitive threshold, as many Republicans are wary of any international limits on U.S. power.