The sanctions target oil giants Rosneft and Lukoil, which between them account for more than 5% of global oil output, and mark a dramatic U-turn by Trump, who said last week that he and Russian President Vladimir Putin would hold a summit in Budapest soon to try to end the war in Ukraine.
The announcement came one day after US President Donald Trump said a planned meeting with his Russian counterpart Vladimir Putin in Budapest would be shelved indefinitely.
