Kamala Harris says Moscow committed crimes against humanity in Ukraine.

Vice President Kamala Harris stressed on Saturday that Russia must be held to account for its “barbaric” actions in Ukraine, telling a security conference in Munich that the United States had formally determined that Moscow’s forces had committed crimes against humanity.

Ms. Harris was among a number of Western officials, including Secretary of State Antony J. Blinken, projecting unwavering resolve in support for Ukraine at the annual Munich Security Conference just days before the first anniversary of Russia’s full-scale invasion.

The vice president noted how, a year earlier at the same conference, she had warned of the imminent Russian invasion of Ukraine. At the time, Ms. Harris said, many wondered how the West would respond and whether Ukraine would be prepared.

“Today, a year later we know: Kyiv is still standing,” she said. “Russia is weakened, the trans-Atlantic alliance is stronger than ever.”

Her remarks emphasized the horrors that have occurred in Ukraine in the past year, invoking images of atrocities carried out by Russian forces in places like Bucha and Mariupol.

Russia’s actions in Ukraine are an “assault on our common values,” Ms. Harris said, describing how Moscow’s forces had carried out “gruesome acts of murder,” torture, rape and deportation in a “widespread and systemic attack against a civilian population.”

Crimes against humanity and war crimes are notoriously difficult to prosecute and prove, but Ms. Harris cited her experience as a prosecutor in saying that “we have examined the evidence” and “there is no doubt” that Russia has committed crimes against humanity in Ukraine.

“I say to all those who have perpetrated these crimes and to their superiors who are complicit in these crimes: You will be held to account,” she said.

Ms. Harris spoke as Russia has been stepping up its offensive in eastern Ukraine, and the vice president acknowledged that Ukrainians and trans-Atlantic unity would continue to be tested.

“There will be more dark days in Ukraine,” she said, adding that if President Vladimir V. Putin of Russia “thinks he can wait us out, he is badly mistaken. Time is not on his side.”

Neither Ms. Harris nor Secretary of State Antony J. Blinken — who issued a statement — referred to Mr. Putin by name when addressing the crimes against humanity determination.

President Biden last March branded Mr. Putin a “war criminal” over civilian deaths in Ukraine. The White House initially walked those comments back, saying that the United States had “not made conclusions” about whether war crimes were being committed in Ukraine and that the matter was the subject of an official legal review. Mr. Blinken later said he agreed with Mr. Biden’s assessment.

In September, a United Nations panel of experts concluded in a damning statement that war crimes had been committed in the conflict — though it said they had not at that point found that violations amounted to crimes against humanity, which involve acts committed “as part of a widespread or systematic attack” against a civilian population.

On Saturday, Mr. Blinken said that crimes against humanity designations were reserved for “the most egregious crimes.” Washington’s emphasis on it now, he said, “underlines the staggering extent of the human suffering inflicted by Moscow on the Ukrainian civilian population” and reflects the United States’ commitment to holding Russian forces and officials accountable.

“There can be no impunity for these crimes,” he said.