The official US declaration that Moscow's troops had violated the laws of conflict comes after Blinken, President Joe Biden and Deputy Secretary of State Wendy Sherman all said it was their personal opinion that war crimes have taken place.
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"Today, I can announce that, based on information currently available, the US government assesses that members of Russia's forces have committed war crimes in Ukraine," Blinken said in a statement.
"Our assessment is based on a careful review of available information from public and intelligence sources," he said.
The decision to issue a formal accusation marks a significant step by the US government after weeks of declining to officially say that the attacks committed against civilians in Ukraine were war crimes. It remains to be seen, however, whether there will be any accountability for those accused of carrying out the alleged crimes, and whether Russian President Vladimir Putin himself will be forced to bear any responsibility.