US President Donald Trump fired four senior government officials appointed by his predecessor early Tuesday and warned "over a thousand more" faced imminent dismissal in a first post on Truth Social since his inauguration.

"My Presidential Personnel Office is actively in the process of identifying and removing over a thousand Presidential Appointees from the previous Administration, who are not aligned with our vision to Make America Great Again," Trump said on the platform.

He named four individuals -- Jose Andres from the President's Council on Sports, Fitness and Nutrition, Mark Milley from the National Infrastructure Advisory Council, Brian Hook from the Wilson Center for Scholars, and Keisha Lance Bottoms from the President's Export Council -- as being immediately dismissed.

"Let this serve as Official Notice of Dismissal for these 4 individuals, with many more, coming soon," the post said.

It concluded with the words "YOU'RE FIRED!", Trump's catchphrase from his days as the boss of the hit TV show "The Apprentice".

Many US government institutions are braced for upheaval in the days and weeks to come if Trump makes good on campaign promises to slash the civil service and improve efficiency -- including threats to shutter entire departments.

The Barron's news department was not involved in the creation of the content above. (AFP)