White House security adviser warns of "catastrophic consequences" for Russia's use of nuclear weapons

Jake Sullivan, White House Security Adviser, said the Kremlin has been given a direct message on the possible outcomes of President Putin's decision to deploy a nuclear weapon.

Sullivan made the remarks in an interview with ABC News on September 25.

"And we have communicated directly, privately to the Russians, at very high levels, that there will be catastrophic consequences for Russia if they use nuclear weapons in Ukraine. We have been clear with them and emphatic with them that the United States will respond decisively, alongside our allies and partners, and we have protected those communications, which we have done privately to the Russians, but they well understand what they would face if they went down that dark road," he said.

At the same time, Sullivan did not disclose the details of the conversation, saying that Washington indicated to the Russians what the consequences would be, but remained sensitive about disclosing it publicly.

He added that the US is taking it seriously and it’s not the first time President Putin has made a nuclear threat in this conflict.

"He started way back in February when Russian takes first rolled across the border brandishing that nuclear card. And that has not deterred us from providing more than $15 billion in weapons to Ukraine, helping them be able to defend their country. And it will not deter us now," Sullivan said.