U.S. President Donald Trump has done a turnaround on sanctions against Russia, taking aim at Russia's two biggest oil companies and the billions of dollars they reap for Moscow's war against Ukraine.

Bulgaria is preparing measures to secure uninterrupted supplies of oil and oil derivatives after the U.S. imposed sanctions on Russia's Lukoil , which runs the country's biggest oil refinery, Energy Minister Zhecho Stankov said on Friday.

President Donald Trump’s sanctions against two of Russia’s largest oil companies come as the European Union passes its 19th package targeting the energy sector.