WATCH: Biden calls Putin ‘a war criminal’ amid Russia’s invasion of Ukraine

Initially, Biden responded, "No," when Fox News reporter Jacqui Heinrich asked if he considers Putin as such, but he later circled back to the reporter and said: "Did you ask me whether I would call … Oh, I, I think he is a war criminal."

The comment comes hours after the president condemned Russia’s invasion of Ukraine, and said that the US would be sending more weapons and "additional security assistance" to the defending country, including anti-aircraft and anti-armor weapons, body armor, drones, and guns.

"Putin is inflicting appalling, appalling devastation and horror on Ukraine, bombing apartment buildings, maternity wards, hospitals. I mean, it's God awful," Biden said. "The world is united in our support for Ukraine and our determination to make Putin pay a very heavy price."

During a press briefing on Wednesday afternoon, White House press secretary Jen Psaki said that Biden's comments "speak for themselves," but noted that a "legal process" is still underway at the State Department.

"He was speaking from his heart and speaking from what we've seen on television, which is barbaric actions by a brutal dictator through his invasion of a foreign country," Psaki said.

Biden's response comes after the US Senate voted unanimously on Tuesday to approve a measure to investigate Putin and other Russian officials for "war crimes" and "crimes against humanity," according to Fox News.

Addressing members of Congress on Wednesday morning, Ukrainian President Volodymyr Zelensky said in an appeal for greater action: "Russia has attacked not just us... it went on a brutal offensive against our values, basic human values, it threw tanks and planes against our freedom against our right to live freely in our own country." He was translated by the American ambassador to Ukraine.