WASHINGTON (Reuters) - The United States on Thursday planned to impose economic sanctions on a wider array of Russian oligarchs and their families, a source familiar with the matter said, in response to Russia's invasion of Ukraine.

       Washington has already hit a variety of oligarchs with asset-blocking sanctions. The source, speaking to Reuters on condition of anonymity, said some significant names would be included in Thursday's actions.

       A second person familiar with the matter confirmed that there will be a number of oligarchs sanctioned on Thursday. The source also said Russian officials close to Putin would likely be among those targeted.

       Washington has so far imposed several rounds of sanctions, including against Putin and the central bank, after Russia's forces invaded Ukraine in the biggest assault on a European state since World War Two. Moscow calls the assault a "special operation."

       The measures have included sanctions against what the U.S. Treasury Department said were Russian "elites," including some with ties to Sberbank, VTB, Rosneft and the Federal Security Service (FSB).

       The U.S. sanctions are expected to overlap with some of those already sanctioned by the European Union.

       (Reporting by Steve Holland, Daphne Psaledakis and Matt Spetalnick; Editing by Chizu Nomiyama)