Secretary of State Antony Blinken and National Security Adviser Jake Sullivan this past weekend warned of “catastrophic” consequences if Russian President Vladimir Putin decides to use nuclear weapons in Ukraine, Axios reported.

“We have been very clear with the Russians publicly, and, as well as privately, to stop the loose talk about nuclear weapons,” Blinken said in an interview on CBS News’ 60 Minutes.

“It's very important that Moscow hear from us and know from us that the consequences would be horrific. And we've made that very clear,” he continued.

Blinken, however, asserted that he wouldn’t “get into what the consequences would be” for Russia. He did confirm that the Biden administration has a plan for such an event, adding that “any nuclear weapons would have catastrophic effects” for the nation using them and others.

Meanwhile, Sullivan told NBC News’ Meet the Press that the consequences “would be catastrophic if Russia went down the dark road of nuclear weapons use.”

When pressed about what those countermeasures would be, Sullivan replied: “In private channels we have spelled out in greater detail exactly what that would mean.”

The two officials made their comments after Kremlin officials reiterated a veiled nuclear threat Putin made in announcing the mobilization of some 300,000 reservists last week. Moscow is also moving to annex occupied areas that are staging votes to join Russia.

If Russia's “territorial integrity” was threatened, “we will certainly use all the means at our disposal” to retaliate, Putin said in an address to his nation last Wednesday.

On Saturday, Russian foreign minister Sergei Lavrov said during a news conference that Russia has “a doctrine for nuclear security which is an open document.”

On Face the Nation on Sunday, Ukrainian president Volodymyr Zelenskyy said he believes that Putin isn’t bluffing.

“He wants to scare the whole world,” Zelenskyy said. “These are the first steps of his nuclear blackmail.”

When asked whether he thought stability in Europe was possible with Putin in power, Zelenskyy replied: “No. I don’t have anything to add. My opinion is no. We have observed this over the years. We don’t see stability.”

According to the Stockholm International Peace Research Institute, a think tank that tracks global nuclear stockpiles, Russia boasts the largest nuclear arsenal in the world with nearly 6,000 nuclear warheads. About 1,500 of them are currently deployed.

Ethen Kim Lieser is a Washington state-based Finance and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.

Image: Reuters.