(Bloomberg) -- US Secretary of State Antony Blinken warned Russian President Vladimir Putin of the consequences his country would face for using a nuclear weapon in the Ukraine war.

“We’ve communicated that very clearly and directly to the Russians, including President Putin,” Blinken said during a wide-ranging interview at Bloomberg’s offices in Washington. “We’re concerned.”

Blinken said Russia’s discussion of Ukraine using a so-called dirty bomb was yet “another fabrication” and that Russia has a “history of projecting,” attributing to others behaviors they are contemplating themselves. He said the rhetoric was “irresponsible.”

A dirty bomb uses conventional explosives to spread radioactive nuclear waste over a limited area. For now, Blinken said the US saw no reason to change its nuclear posture.

Blinken pledged continued US support for the Ukrainians, calling it “important” and “necessary” for the US and its allies to “stick with Ukraine.” 

He acknowledged that the energy transition under way in Europe is challenging and “not without pain” but said the US is prepared to support governments there through several initiatives, including an increase in production of US oil and gas and efforts to keep prices “in check,” including further releases from the Strategic Petroleum Reserve.

--With assistance from Jonathan Tirone and Matthew Martin.

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