The US president called Putin a “crazy SOB” during a fundraiser in San Francisco, warning there is always the threat of nuclear conflict but that the existential threat to humanity remains climate.

“This is the last existential threat. It is climate. We have a crazy SOB like that guy Putin and others and we always have to worry about nuclear conflict, but the existential threat to humanity is climate,” Biden told a small group of donors on Wednesday.

Biden is on a three-day tour of the West Coast that has included fundraisers in Southern and Northern California, events that will add to the US$130 million that his campaign had amassed as of the end of January.

Putin says he prefers more ‘predictable’ Biden over Trump

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.”

Biden has previously cursed “son of a b***” at others. In January 2022, he was caught on the hot mic using the same term of abuse against a Fox News White House reporter.

Biden has a tendency to go off script during election fundraisers and in recent months has dug into the Chinese government, the Republican Party and US ally Israel for its bombing of the Gaza Strip.

Biden’s verbal attacks against Putin have also sharply intensified at the White House and on the campaign trail. Last week, the US president blamed Putin and “his thugs” for the death of opposition leader Alexei Navalny.

Biden’s has previously called the Russian president, who ordered the invasion of Ukraine in 2022, a “butcher” and a “war criminal”.

“We don’t know exactly what happened, but there is no doubt that the death of Nalvany was a consequence of something that Putin and his thugs did,” Biden said at the White House after Russian prison officials announced that Navalny had died.

The Kremlin has denied involvement in Navalny’s death and said Western claims that Putin was responsible are unacceptable.

Biden and Putin remain deeply at odds over Russia’s invasion of Ukraine two years ago, over which Russia has been sanctioned by the United States and other Western nations. Biden’s reactions have put a further chill into already bitter US-Russian relations.

On Tuesday, Biden said the US will announce a major package of sanctions against Russia over Navalny’s death and the Ukraine war.

Biden’s expected Republican opponent in November, former president Donald Trump, has expressed admiration for Putin both during his 2017-2021 White House tenure and afterward.

However, he also recently compared himself to Navalny, implying that they both had faced politically motivated prosecutions.

Trump was fined US$350 million after a New York judge found he lied for years about his wealth on financial statements in his companies. Trump said the ruling was a form of “communism or fascism”.

“Some of the things that this fellow’s been saying, like he’s comparing himself to Navalny and saying that – because our country’s become a communist country, he was persecuted, just like Navalny was persecuted. I don’t know where the hell this comes from,” Biden said.

“I mean, if I stood here 10, 15 years ago and said any of this, you’d all think I should be committed,” he said. “It astounds me.”

“I’ve been around a long time and I’ve never quite seen a crowd like this MAGA Republican crowd,” Biden added, referring to Trump’s “Make America Great Again” slogan. “They seem to have very little moral compass on what is important to people.”

Reuters, Associated Press and Bloomberg