Oil is all Russia's economy has left following its invasion of Ukraine earlier this year, according to Amos Hochstein, special presidential coordinator for President Joe Biden.
"Oil is the only thing they have left in that economy … Putin has destroyed the rest of the economy," Hochstein told CNBC's Hadley Gamble Monday.
"All he's got left is the stuff that comes out of the ground.
He won't sell his gas to Europe anymore, so all he has is oil, so that's what funds this war."
The Russian economy shrunk by 4% year-on-year over the second quarter, and the Central Bank of Russia expects the downturn to deepen in the quarters ahead.