US President Joe Biden on Wednesday called Russian President Vladimir Putin a "war criminal", the harshest condemnation of Putin's actions from any US official since the war in Ukraine began three weeks ago.
"I think he is a war criminal," Biden told reporters after remarks at the White House, according to CNN.
Kremlin spokesman Dmitry Peskov said the comment was "unacceptable and unforgivable rhetoric," reported the Tass news agency.
The shift from the administration's previous stance came after an emotional address to Congress from Ukrainian President Volodymyr Zelenskyy, who aired a video showing Ukrainians suffering amid Russia's onslaught. Zelenskyy asked American lawmakers and Biden for more help defending itself, including a no-fly zone and fighter jets.
Biden later announced out new American military assistance to Ukraine, including anti-aircraft and anti-armor systems, weapons and drones, though he stopped short of acceding to Zelensky's requests.
US officials, including Biden, had previously avoided saying war crimes were being committed in Ukraine, citing ongoing investigations into whether that term could be used, noted CNN.
Other world leaders have not been as circumspect, including British Prime Minister Boris Johnson, who said last week war crimes were being committed.
The International Criminal Court’s prosecutor, Karim Khan, officially opened an investigation two weeks ago into possible war crimes, crimes against humanity or genocide in Ukraine.
The probe will cover crimes dating back to 2013, but will also cover the conflict sparked by Russia’s invasion of Ukraine.
After Biden delivered his assessment on Wednesday, the White House said the administration's investigation into war crimes would continue.
"The President's remarks speak for themselves," press secretary Jen Psaki said, adding that Biden was "speaking from the heart."