The rhetorical clash between the United States and Russia escalated on Wednesday when President Biden said that he believed President Vladimir V. Putin of Russia was a “war criminal,” and a top Russian official said the comment was “unacceptable and unforgivable.”
Mr. Biden was responding to a reporter’s question as he was leaving an event at the White House. Later, the White House press secretary, Jen Psaki, told reporters that Mr. Biden was “speaking from his heart and speaking from what he’s seen on television.”
In the weeks since Russia invaded Ukraine, there have been attacks on refugee escape routes, heavily populated civilian neighborhoods, schools, hospitals and, on Wednesday, a theater that was being used as a bomb shelter.
On Wednesday, an International Criminal Court prosecutor, Karim Khan, held a virtual meeting with President Volodymyr Zelensky while in Ukraine. Late last month, Mr. Khan said he was seeking authorization to open an investigation into the war, and that his office had already found “a reasonable basis” to believe war crimes had been committed. He said it “had identified potential cases that would be admissible.”
The Kremlin responded to Mr. Biden’s comment on Wednesday with a longstanding critique that it was Western countries, rather than Russia, who were threatening world peace.
Dmitri Peskov, a spokesman for Mr. Putin, told the state-run news outlet Tass that Mr. Biden’s remarks were “unacceptable and unforgivable on the part of the head of a state, whose bombs have killed hundreds of thousands of people around the world.”
Last month, Mr. Putin spoke to reporters in his country about “the fundamental threats which irresponsible Western politicians created for Russia consistently rudely and unceremoniously from year to year.”
Mr. Biden’s unscripted remarks on Wednesday echo messages U.S. officials have been making recently.
Vice President Kamala Harris was in Warsaw on March 10, a day after an apparent Russian strike destroyed a maternity ward in Mariupol. Would the United States support an investigation into accusations Russia committed war crimes, a reporter asked Ms. Harris.
“Absolutely,” Ms. Harris said, though she did not directly accuse Russia of committing war crimes.
Later that same day, the U.S. ambassador to the United Nations, Linda Thomas-Greenfield, told the BBC NewsHour that Russia’s attacks on civilians “constitute war crimes; there are attacks on civilians that cannot be justified by any — in any way whatsoever.”
Mr. Biden has long criticized Mr. Putin, including in a television interview with ABC News that was broadcast last year. In the interview, when Mr. Biden was asked whether he thought Mr. Putin was a “killer,” he responded, “Mmm hmm, I do.”
The Kremlin recalled its ambassador to Washington after those remarks aired, and Mr. Putin quoted a Russian schoolyard rhyme in response, saying, “When I was a child, when we argued in the courtyard, we said the following: ‘If you call someone names, that’s really your name.’”