"I will gather strength from this," he added.

Holding a press conference in Miami before reporting to prison, former Trump advisor Peter Navarro said the justice system in the US will "have done a crippling blow to the constitutional separation of powers and executive privilege."

Navarro also criticized the "emergence of lawfare and the partisan weaponization of our justice system, which we have seen done to this country with a vengeance since the coming of Donald John Trump as president."

"I am the first senior White House advisor in the history of our republic that has ever been charged with this alleged crime," Navarro said. Navarro was sentenced to four months in prison for contempt of Congress for not complying with the subpoena due to executive privilege.

"When I received that congressional subpoena…I had an honest belief that the privilege had been invoked," he told US District Judge Amit Mehta in the January sentencing hearing.

"I saw alleged because for hundreds of years this has not been a crime. And for 50 years, the Department of Justice has maintained the principle of absolute testimony immunity, and it was only with my case that somehow that has changed."

"And an executive privilege goes back to George Washington and his remarks to the Congress regarding the Jay Treaty and he said, very simply and clearly, succinctly, elegantly, that to write to the Congress he said, I cannot command you as members of Congress to come to be, you cannot command me to come to you."