The United States is threatening Russia after the former Soviet Union threatened to use nuclear weapons to protect Russia and its territories. The U.S. said Russia will suffer “catastrophic consequences” if they deploy weapons of mass destruction.

“Any use of nuclear weapons will be met with catastrophic consequences for Russia,” national security adviser, Jake Sullivan, told CBS on Sunday. Sullivan also said on the network’s Face the Nation program that the Biden administration had told Moscow both privately at “very high levels” and publicly that “the United States and our allies will respond decisively if Russia uses nuclear weapons.”

He also declared that the referendums in the Donbass republics and Kherson and Zaporozhye Regions of Ukraine had not altered Washington’s support for Kyiv. Sullivan added that Washington was keeping “a close eye” on the Zaporozhye nuclear plant. In order to lessen the chance of a catastrophic incident, the facility has been placed in a cold shutdown in response to constant shelling that both sides blame on each other.

The International Atomic Energy Agency, visited the site of the nuclear plant earlier this month and identified an “urgent need for interim measures to prevent a nuclear accident,” specifically the “immediate establishment of a nuclear safety and security protection zone.” The IAEA, however, failed to mention the culprit behind the attacks, despite Russia providing evidence that pointed to the Ukrainian side.

Russia has also said they are not “bluffing” when it claims it will use nuclear weapons to defend itself.

Russian Nukes Can Be Used To Defend Annexed Ukraine Regions, Kremlin Warns