The Biden administration has introduced its most extensive sanctions package yet, targeting Russia’s oil and gas revenues in an effort to cripple Moscow’s primary source of funding for its war in Ukraine. The conflict, which began with Russia’s invasion in February 2022, has resulted in over 12,300 civilian deaths and left cities in ruins.

The U.S. Treasury announced on Friday that the sanctions will affect major Russian energy companies, including Gazprom Neft and Surgutneftegas, as well as 183 vessels involved in transporting Russian oil. Many of these ships are part of the so-called “shadow fleet”—older tankers operated by non-Western companies that have facilitated oil shipments to India, China, and other markets since the Group of Seven imposed a price cap in 2022.

The sanctions aim to disrupt every step of Russia’s oil production and distribution chain. The Treasury also closed a loophole that had allowed energy payments to flow through sanctioned Russian banks, tightening restrictions further. U.S. officials estimate that, if enforced rigorously, the measures could cost Russia billions of dollars each month.

Ukrainian President Volodymyr Zelensky welcomed the sanctions, expressing optimism about their impact. On X (formerly Twitter), Zelensky stated that the measures would “deliver a significant blow” to Russia’s ability to fund its war effort. “The less revenue Russia earns from oil … the sooner peace will be restored,” he added.

Daleep Singh, a senior economic and national security adviser at the White House, called the sanctions “the most significant yet” against Russia’s energy sector. He emphasized their comprehensive scope, describing them as a critical tool in weakening Russia’s war machine and bolstering Ukraine’s resistance.

Gazprom Neft dismissed the sanctions as “unjustified and illegitimate.” Despite these objections, the Biden administration views the measures as essential to curbing Moscow’s aggression and holding it accountable for the ongoing conflict.

As the U.S. prepares for the transition to President-elect Donald Trump’s administration, the sanctions are designed to strengthen Ukraine’s position in potential peace negotiations while continuing to exert financial pressure on Russia.

This latest sanctions package underscores the international community’s commitment to reducing Russia’s ability to sustain the conflict. By targeting the core of Moscow’s economic power, the Biden administration aims to support Ukraine’s fight for sovereignty and push closer to a resolution of the devastating war.