"Our point of view is that this is further indication of Putin's desperation to sustain his war of aggression against Ukraine, despite it being a major drain on the Russian economy and the heavy losses of Russian troops, with some estimates as high as 315,000 casualties," State Department spokesman Vedant Patel told reporters.

"The Kremlin's mobilization of its war of aggression against Ukraine has caused so many families to suffer," he said.

"Russia started this unprovoked war against Ukraine. Putin could end it at any time by withdrawing his forces from Ukraine."

Putin, starting an unprecedented fifth term as president, removed veteran defense minister Sergei Shoigu and replaced him with a top economic official and technocrat, Andrei Belousov.