Russian President Vladimir Putin
Russian President Vladimir PutinReuters

Between two and four thousand Russian soldiers have been killed in the war between Russia and Ukraine so far, according to CIA head William Burns, a far cry from the figure of around 500 fatalities released by the Russian Defense Ministry last week.

Burns, speaking at a House of Representatives intelligence committee hearing, revealed that the United States had pursued "intensive intelligence sharing" with Ukraine and continues to do so, informing Ukrainian leaders of Russian military plans and other pertinent details.

Reuters news agency cited Burns' assessment that Russian President Putin would not back down, even if he fails to take control of the Ukrainian capital of Kyiv, which Burns predicted would be the case.

"I think Putin is angry and frustrated right now," Burns said. "He’s likely to double down and try to grind down the Ukrainian military with no regard for civilian casualties. I fail to see how he can produce that kind of an end game and where that leads, I think, is for an ugly next few weeks in which he doubles down ... with scant regard for civilian casualties."