The Kremlin said on Thursday a remark by Joe Biden calling Russian President Vladimir Putin a "crazy SOB" debased the United States and those who use such vocabulary, and was a poor attempt to appear like a "Hollywood cowboy".

The U.S. president made the comment during a fundraiser in San Francisco on Wednesday, and also said there was always a threat of nuclear conflict although the existential threat to humanity remained the 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," Peskov said.

He later added in comments to a state television reporter: "This is a disgrace for the country itself, I mean the United States."

The war in Ukraine, the death of Russian opposition leader Alexei Navalny and U.S. assertions that Russia plans to put a nuclear weapon in space have led to the biggest crisis in relations between Russia and the West since the Cold War.

Some Russian and U.S. diplomats say they do not remember a time when relations between the world's two biggest nuclear powers were worse, including during the 1962 Cuban Missile Crisis.

Biden said last week after prison officers announced Navalny's death in a Russian penal colony that it was "a consequence of something that Putin and his thugs did." Navalny had previously accused Putin of trying to kill him, an allegation the Kremlin denied.

Russian officials say the West rushed to blame Putin without waiting for evidence. The Kremlin says the West's reaction to Navalny's death is unacceptable and unjustified.

Biden said in a speech in Warsaw in 2022 that Putin "cannot remain in power". The White House played down the remark, while hardliners in Russia saw it as evidence that the U.S. wanted to topple Putin.

In 2021, Biden said he thought Putin a killer. Putin said Biden phoned him later to give an explanation of why he used such words.