NASA in August, during President Joe Biden's administration, deemed Starliner too risky to bring them back to Earth and tapped SpaceX to return them on a Crew Dragon spacecraft.
That craft is already docked with the space station, having flown there for NASA's Crew-9 astronaut rotation mission in September with empty seats for Wilmore and Williams.
The astronauts' original February departure date on Crew-9 was delayed to late March because SpaceX needed more time "to complete processing" of a new Crew Dragon capsule that will replace theirs for the Crew-10 mission, NASA said in December.
The agency has a delicately coordinated ISS schedule, and an early return might leave the station's U.S. contingent understaffed.
It was unclear whether Trump's demand would mean NASA bringing Crew-9 back to Earth before the Crew-10 capsule arrives, or SpaceX launching Crew-10 earlier than planned.