(AFP) - Russian President Vladimir Putin on Thursday signed a law revoking Russia's ratification of the Comprehensive Nuclear Test Ban Treaty, a move strongly criticised by the United States.

The 1996 treaty outlaws all nuclear explosions, including live tests of nuclear weapons, though it never came into force because some key countries -- including the United States and China -- never ratified it.

The West has accused Russia of using reckless nuclear rhetoric since it launched its offensive on Ukraine last February.

US Secretary of State Antony Blinken criticised Putin's announcement on Thursday, and called on Moscow to commit to not carry out testing.

"Unfortunately, it represents a significant step in the wrong direction, taking us further from, not closer to, entry into force" of the treaty, Blinken said in a statement.

"This continues Moscow's disturbing and misguided effort to heighten nuclear risks and raise tensions as it pursues its illegal war against Ukraine," he said.

Putin last week oversaw ballistic missile drills in what Defence Minister Sergei Shoigu said was practice for a "massive" retaliatory nuclear strike against an unnamed enemy.

Putin also said last month he was "not ready to say" whether Russia would carry out live nuclear tests.

- 'Deeply regrettable' -

The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) has urged Russia to continue its commitment to the treaty, including the use of monitoring stations capable of detecting the slightest explosion in real time.

"Today's decision by the Russian Federation to revoke its ratification of the Comprehensive Nuclear-Test-Ban Treaty is very disappointing and deeply regrettable," CTBTO head Robert Floyd said on X, formerly known as Twitter.

France, one of the treaty's original signatories, said it "deplored" Russia's decision to revoke the ratification.

"Russia's decision compromises the work of making the treaty universal. We reaffirm the importance of the CTBT and its full implementation," it said.

The bill to revoke the treaty passed through Russia's parliament last month in a fast-track process.

During parliamentary hearings, State Duma speaker Vyacheslav Volodin said the move to revoke the treaty was a response to the United States' "cynicism" and "boorish attitudes" on nuclear weapons.

Although it never entered into force, the agreement was ratified by 178 countries, including nuclear powers Russia, France and Britain, and has symbolic value.

The United States as well as China have never ratified the treaty, a key obstacle for it coming into force.

President George H.W. Bush in 1992 signed into law a unilateral ban on US nuclear testing that has since been extended. But the Senate rejected ratifying the test ban treaty in 1999.

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

The treaty's backers say it established an international norm against live tests of nuclear weapons, but critics say the potential of the deal remains unrealised without the ratifications of major nuclear powers.

Russia's parliament ratified the agreement in June 2000, six months after Putin first became president.

© Agence France-Presse