White House chief of staff John Kelly has the full authority of the president to begin firing staff that aren't fully committed to the administration's directives, said President Trump's former campaign chief and informal adviser on Sunday.

The rule is to put country first, Trump second and personal ambition last, Corey Lewandowski told Fox News. "And if anybody doesn't follow that rule, I think Gen. Kelly has been very sure about the fact that he has the full authority of the president to dismiss any staff that isn't willing to follow the president's agenda."

Kelly, who began his role as chief of staff at the beginning of last week, reportedly told a group of 200 White House staffers something similar on Friday.

Lewandowski said "this is a much-needed change," which is also part of a serious crack down on leaked classified information.

He said that Kelly, together with Attorney General Jeff Sessions, will "continue to find who these leaks are" with the hope they are prosecuted.

"I hope they put them in handcuffs and walk them out the door," Lewandowski said. "And make a very clear determination to their colleagues that this will not be tolerated."