President-elect Donald Trump said on Tuesday he picked Republican Representative Mike Waltz to be his national security adviser, tapping a retired Army Green Beret who has been a leading critic of China.

Trump also announced that former Director of National Intelligence John Ratcliffe will head the Central Intelligence Agency (CIA) under his administration.

"From exposing fake Russian collusion to be a Clinton campaign operation, to catching the FBI's abuse of Civil Liberties at the FISA Court, John Ratcliffe has always been a warrior for Truth and Honesty with the American Public," Trump said.

"When 51 intelligence officials were lying about Hunter Biden's laptop, there was one, John Ratcliffe, telling the truth to the American People," he added.

"For these and many other reasons, it was my great honour in 2020 to award John the National Security Medal, the nation's highest honour for distinguished achievement in the field of Intelligence and National Security," he said.

Ratcliffe previously served as the sixth director of National Intelligence (DNI). In this role, he served as the leader of the US intelligence community and principal intelligence advisor to President Trump in his first term.

"I look forward to John being the first person ever to serve in both of our nation's highest Intelligence positions. He will be a fearless fighter for the Constitutional Rights of all Americans, while ensuring the Highest Levels of National Security, and PEACE THROUGH STRENGTH," he said.

Prior to his nomination and confirmation as DNI, Ratcliffe served in Congress for over five years as the US Representative for the 4th Congressional District of Texas. As a Congressman, he was a leading policy maker on national security issues as a member of the House Intelligence and Judiciary Committees and as Cybersecurity Chairman on the Homeland Security Committee.