The Kremlin on Thursday said it was a "huge shame" that US President Joe Biden had called Russian counterpart Vladimir Putin a "crazy SOB".
Biden made the comments at a speech in San Francisco attended by a small group of reporters, in which he contrasted the risk posed by Putin to the threat of climate change.
"This is a huge shame for the country itself... for the US. If a president uses that kind of language, it's shameful," Putin's spokesman Dmitry Peskov said.
"It is clear that Mr Biden is demonstrating Hollywood cowboy style behaviour to serve domestic political interests," he continued.
Biden has a history of similar hot-mic comments and has been strongly critical of Putin before, announcing in 2022 that the Kremlin chief "cannot remain in power".
His remarks come as relations with the Kremlin linger at historic lows over the conflict in Ukraine and the death of Russian opposition leader Alexei Navalny in jail.
The US President has promised to introduce tough new sanctions against Moscow over Navalny's death, which the White House has blamed on the Kremlin.
IOL