He said: “Unacceptable and unforgivable on the part of the head of a state, whose bombs have killed hundreds of thousands of people around the world.”
White House Press Secretary Jen Psaki said the President had been “speaking from the heart” when making the comment.
Ms Paski added that Mr Biden had made the comment after seeing “barbaric” footage of the violence in Ukraine rather than making an official declaration.
It comes after Ukrainian President Volodymyr Zelensky made a virtual appearance in the US Congress appealing for help and a no-fly zone over his country.
Mr Zelensky also compared the Russian invasion of Ukraine to the September 11 attacks in the United States.
Vladimir Putin has not limited his backlash to his American counterpart, however.
Speaking overnight, the Russian President blasted Russians who didn’t back the invasion in Ukraine.
Putin argued Russians “will always be able to distinguish true patriots from scum and traitors and will simply spit them out like a gnat that accidentally flew into their mouths”.
READ MORE: Putin Shambles: Russian forces routed – column wiped out VIDEO
He said: “I am not at all judging those who have a villa in Miami or the French Riviera, who cannot do without foie gras, oysters or so-called gender freedoms.
“The problem is absolutely not in this, but I repeat, in the fact that many of these people, by their very nature, are mentally located precisely there, and not here, not with our people, not with Russia.
“This is what they think – in their opinion – a sign of belonging to a higher caste, to a higher race.”