President Joe Biden has authorized the use of U.S.-supplied long-range missiles by Ukraine to strike even deeper inside Russia, the latest easing of limitations meant to prevent the conflict from further spiraling, according to one U.S. official and three people familiar with the matter.

The decision allowing Ukraine to use the Army Tactical Missile System, or ATACMs, for attacks farther into Russia comes as thousands of North Korean troops have been sent into a region along Ukraine’s northern border to help Russia retake ground and as President-elect Donald Trump has said he would bring about a swift end to the war, expressing skepticism over continued support by the United States.