WASHINGTON—The Trump administration is ready to block a Russian state-owned oil giant from gaining control of critical energy assets in the U.S. owned by Venezuela, senior American officials say, a move that likely would feed tensions between Washington and Moscow.

Petróleos de Venezuela SA offered Russia’s PAO Rosneft nearly half of the shares of its U.S.-based subsidiary Citgo Petroleum Corp. as collateral for $1.5 billion in loans the Russian firm made in 2016 to help prop up cash-starved PdVSA and its owner, the Venezuelan...