U.S. Ambassador Linda Thomas-Greenfield gave an impassioned speech in front of the U.N. General Assembly on Wednesday.
She called on Russia to stop its "unprovoked, unjustified, unconscionable war."
"We have seen videos of Russian forces moving exceptionally lethal weaponry into Ukraine, which has no place on the battlefield. That includes cluster munitions and vacuum bombs – which are banned under the Geneva Convention," she said.
Thomas-Greenfield pinned the blame directly on Russian President Vladimir Putin. She said it was his choice alone to start the war, which has led to the deaths of innocent people and a humanitarian crisis.
"It was his choice to force hundreds of thousands of people to stuff their lives into backpacks and flee the country, to send newborn babies into makeshift bomb shelters, to make children with cancer huddle in hospital basements, interrupting their treatments, essentially sentencing them to death," she said.
Thomas-Greenfield's speech came hours before the U.N. General Assembly voted to demand that Russia stop its offensive in Ukraine and withdraw all troops.
The vote Wednesday was 141 to 5, with 35 abstentions.
The countries voting with Russia included North Korea, Syria, Eritrea and Belarus.