Biden said this on February 21 during an election campaign in San Francisco, The Hill reports.
"This is the last existential threat, it is climate. We have a crazy SOB like that guy, Putin, others. And we always have to be worried about a nuclear conflict. But the existential threat to humanity is climate," the US president said.
In this context, Biden also directly blamed Putin for Navalny's death and sharply criticized former President Donald Trump, who has avoided mentioning Putin in his reaction to the Russian opposition leader's death. Biden also said that the Republicans once had "American moral center, but that seems to be lost".
Russian presidential spokesman Dmitry Peskov called Biden's statement a disgrace to the United States.
"As the press secretary of the Russian president, I can say that such boorish statements from the mouth of the US head of state are unlikely to offend the head of another state, let alone President Putin. But this is a huge disgrace for the country itself, I mean for the United States of America," Peskov was quoted as saying by Interfax.
"If the president of such a country uses such vocabulary, well, it should be a shame. It's clear that Mr. Biden is demonstrating Hollywood cowboy-style behavior for domestic political interests, he would like to do that very much, I don't think it's possible," he added.
Peskov noted that Putin has never publicly insulted Biden.
Putin also reacted to Biden's remarks. He said that he had recently voiced the opinion that Biden would be a better president for Russia than Trump.
"And judging by what he (Biden - ed.) has now said, I was absolutely right — this is an adequate reaction to my words."