MOSCOW (AP) — Russia will no longer give the United States (US) advance notice about its missile tests as envisioned under a nuclear pact the Kremlin has suspended, a senior Moscow diplomat said Wednesday, as its military rolled missile launchers across Siberia in a show of the country’s massive nuclear capability amid fighting in Ukraine.

Deputy Foreign Minister Sergei Ryabkov told Russian news agencies that Moscow has halted all information exchanges with Washington under the last remaining nuclear arms treaty with the US after suspending its participation in it last month.

Along with the data about the current state of the countries’ nuclear forces routinely released every six months in compliance with the New START treaty, the parties also have exchanged advance warnings about test launches and deployments of their nuclear weapons. Such notices have been an essential element of strategic stability for decades, allowing Russia and the United States to correctly interpret each other’s moves and make sure that neither country mistakes a test launch for a missile attack.

The termination of information exchanges under the pact marks yet another attempt by the Kremlin to discourage the West from ramping up its support for Ukraine by pointing to Russia’s massive nuclear arsenal. In recent days, President Vladimir Putin announced the deployment of tactical nuclear weapons to the territory of Moscow’s ally Belarus.

Putin suspended the New START treaty last month, saying Russia can’t accept U.S. inspections of its nuclear sites under the agreement at a time when Washington and its NATO allies have openly declared Moscow’s defeat in Ukraine as their goal. Moscow emphasised that it wasn’t withdrawing from the pact altogether and would continue to respect the caps on nuclear weapons the treaty set.

It wasn’t immediately clear whether Ryabkov’s statement indicated Moscow’s intention to terminate all warnings about missile tests or just those envisioned by the New START treaty. Moscow and Washington have exchanged notifications about test launches of ballistic missiles since the Cold War era, and the Foreign Ministry said last month that Russia will keep issuing them in line with a 1988 US-Soviet agreement.

“There will be no notifications at all,” Ryabkov said in remarks reported by Russian news agencies when asked if Moscow would also stop issuing notices about planned missile tests. “All notifications, all kinds of notifications, all activities within the framework of the treaty will be suspended and will not be conducted regardless of what position the US may take.”

US State Department deputy spokesman Vedant Patel said the Biden administration was aware of Ryabkov’s comments but it has not “received any notice indicating a change.”

He added that Washington has “across-the-board concerns about Russia’s reckless behaviour as it relates to the New START treaty.”

Heather Williams, director of the Project on Nuclear Issues at the Center for Strategic and International Studies, a Washington think-tank, said Russia’s rhetoric was concerning but fits a pattern of behaviour related to Ukraine.

”They use nuclear weapons to turn up the volume on a lot of their other activities, and arms control treaties are just the latest way for Russia to try to advance its goals in Ukraine,” she said.

Of more concern, Williams said, is that the collapse of New START has caused a severe reduction in communications between Washington and Moscow, which could be dangerous. “One of the biggest tragedies of the breakdown in New START is the loss of the communication channel,” she said.

Pavel Podvig, an expert on Russian nuclear forces, tweeted that Ryabkov’s reference to the termination of notices in the context of the New START indicated that Russia will keep issuing them in conformity with the 1988 pact.

Ryabkov’s announcement followed US officials’ statement that Moscow and Washington have stopped sharing biannual nuclear weapons data that were envisioned by the New START treaty. Officials at the White House, Pentagon and State Department said the US had offered to continue providing this information to Russia even after Putin suspended its participation in the treaty, but Moscow told Washington it would not be sharing its own data.

The New START, signed in 2010 by then-Presidents Barack Obama and Dmitry Medvedev, limits each country to no more than 1,550 deployed nuclear warheads and 700 deployed missiles and bombers. The agreement envisages sweeping on-site inspections to verify compliance.