MOSCOW: The Kremlin on Thursday said Joe Biden's remark about President Vladimir Putin debased the United States and those who use such vocabulary - and was a poor attempt to appear like a "Hollywood cowboy".

Biden called Putin a "crazy SOB" during a fundraiser in San Francisco on Wednesday, warning there is always the threat of nuclear conflict but that the existential threat to humanity remains climate.

"The use of such language against the head of another state by the president of the United States is unlikely to infringe on our president, President Putin," Kremlin spokesman Dmitry Peskov said.

"But it debases those who use such vocabulary."

Peskov said the remark was "probably some kind of attempt to look like a Hollywood cowboy. But honestly I don't think it's possible."

"Has Mr. Putin ever used one crude word to address you? This has never happened. Therefore, I think that such vocabulary debases America itself."