US President Donald Trump has appointed immigration hardliner Stephen Miller as his new White House chief of staff, replacing Susie Wiles following significant Republican losses in the midterm elections.

WASHINGTON: US President Donald Trump on Friday named Stephen Miller, architect of his hardline immigration policy, as his new chief of staff, signaling a bare-knuckle fightback after Republicans were hammered in the midterms.

Ultra-loyalist Miller, 41, will replace Susie Wiles, who becomes the first major White House casualty from the Democratic landslide earlier this week.

Democrats pledged they would fight “every step of the way” against Miller, who became synonymous with scenes of masked immigration agents committing violence after he backed federal agents who shot and killed two Americans.