A senior Russian diplomat said Wednesday that Moscow will no longer inform the U.S. about its missile tests, an announcement that came as the Russian military deployed mobile launchers in Siberia in a show of the country’s massive nuclear capability amid the fighting in Ukraine.

Russian Deputy Foreign Minister Sergei Ryabkov said in remarks carried by Russian news agencies that Moscow has halted all information exchanges with Washington after previously suspending its participation in the last remaining nuclear arms pact with the U.S.

Last month, Russian President Vladimir Putin suspended the New START treaty, charging that 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 Russia’s defeat in Ukraine as their goal.

Moscow emphasized that it wasn’t withdrawing from the pact altogether and would continue to respect the caps on nuclear weapons the treaty set.

The Russian Foreign Ministry initially said Moscow would keep notifying the U.S. about planned test launches of its ballistic missiles, but Ryabkov’s statement reflected a change of course.

“There will be no notifications at all,” Ryabkov said when asked if Moscow would also stop issuing notices about planned missile tests. “All notifications, all kinds of notifications, all activities under the treaty. will be suspended and will not be conducted regardless of what position the U.S. may take.”

As part of the Russian drills that began Wednesday, Yars mobile missile launchers will maneuver across three regions of Siberia, Russia’s Defense Ministry said. The movements will involve measures to conceal the deployment from foreign satellites and other intelligence assets, the ministry said.

The Defense Ministry didn’t say how long the drills would last or mention plans for any practice launches. The Yars is a nuclear-tipped intercontinental ballistic missile with a range of about over 6,800 miles. It forms the backbone of Russia’s strategic missile forces.

The Defense Ministry released a video showing massive trucks carrying the missiles driving out from a base to go on patrol. The maneuvers involve about 300 vehicles and 3,000 troops in eastern Siberia, according to the ministry.

The massive exercise took place days after Russian President Vladimir Putin announced a plan to deploy tactical nuclear weapons to Belarus, Russia’s neighbor and ally.

Tactical nuclear weapons are intended for use on the battlefield and have a relatively short range and a much lower yield compared to the long-range strategic missiles fitted with nuclear warheads that are capable of obliterating whole cities.

Nuclear Weapons in Belarus

Putin’s decision to put the tactical weapons in Belarus followed his repeated warnings that Moscow was ready to use “all available means” — a reference to its nuclear arsenal — to fend off attacks on Russian territory.

Russian officials have issued a barrage of hawkish statements since their troops entered Ukraine, warning that the continuing Western support for Ukraine raised the threat of a nuclear conflict.

In remarks published Tuesday, Nikolai Patrushev, the secretary of Russia’s Security Council, which Putin chairs, warned the United States and its allies against harboring hopes for Russia’s defeat in Ukraine.

Patrushev alleged that some American politicians believe the U.S. could launch a preventative missile strike on Russia to which Moscow would be unable to respond, a purported belief that he described as “short-sighted stupidity, which is very dangerous.”

“Russia is patient and isn’t trying to scare anyone with its military superiority, but it has unique modern weapons capable of destroying any adversary, including the United States, in case of a threat to its existence,” Patrushev said.