The Biden administration delivered a parting blow to Russia’s economy Friday, targeting two of its largest oil companies and 183 oil tankers in what a senior official called the “most significant sanctions yet against the Russian energy sector, the largest source of revenue for the Kremlin’s war machine.”

The Biden administration has imposed extensive sanctions on Russia’s oil and gas sector to weaken its revenues amid the ongoing war in Ukraine. This includes targeting major companies and vessels involved in Russian oil production and trade.

The Biden administration on Friday targeted Russia’s energy sector, including its oil industry, with some of its harshest sanctions to date meant to cut off funding for Moscow’s war against Ukraine.