U.S. President Donald Trump ousted his national security adviser Mike Waltz on Thursday and named Secretary of State Marco Rubio as his interim replacement in the first major shakeup of Trump's inner circle since he took office in January, Reuters reported.

Trump, in a social media post, said he would nominate Waltz to be the next U.S. ambassador to the United Nations, adding that "he has worked hard to put our nation's interests first."

Earlier in the day, multiple sources said Trump had decided to remove Waltz from his national security post. The retired Army Green Beret and former Republican lawmaker from Florida had faced criticisminside the White House, particularly after he was caught up in a March scandal involving a Signal chatamong top Trump national security aides.

Rubio will be the first person since Henry Kissinger in the 1970s to hold the positions of secretary of state and national security adviser simultaneously, according to Reuters.