Some 15,000 troops have already died on the Russian side since Moscow invaded Ukraine, according to estimates by the head of US Central Intelligence Agency.
About three times as many Russians are believed to have been injured since the start of the war on February 24, CIA director William Burns said during a security conference in the US city of Aspen.
“The Ukrainians have suffered as well, probably a little less than that,” Burns said on Wednesday evening.
Russia has not disclosed any current figures on casualties on its side.
Burns said the massing of Russian forces in the eastern Donbass region, which includes Luhansk and Donetsk, suggests, at least for now, that the Russian military has learned from its failures at the beginning of the war.
Early in the invasion, Russia attempted to take over the Ukrainian capital Kiev, but without success.
He explained that in some ways, the Russian troops have moved back into a move comfortable position, using its advantage and long-range firepower to effectively destroy Ukrainian targets.
