US President Donald Trump has replaced Mike Waltz as national security adviser and said that he is nominating him to be the next US Ambassador to the United Nations.
Mr Trump also said in a social media post that Secretary of State Marco Rubio will serve as interim national security advisor.
Four people briefed on the matter previously told Reuters that Mr Waltz is being forced out of his job.
Mr Waltz and his deputy Alex Wong are both set to leave their posts, CBS News reported, while Fox News said Mr Trump was expected to comment on the matter soon.
A White House official did not confirm the reports to Reuters, saying they "do not want to get ahead of any announcement".
A 51-year-old former Republican politician from Florida, Mr Waltz faced criticism inside the White House when he was caught up in a March scandal involving a Signal chat among top Trump national security aides.
It was not immediately clear who would take over from Mr Waltz, but one option included US special envoy Steve Witkoff, who has been involved in both Russia-Ukraine diplomacy as well as the Middle East, one of the sources said.
The National Security Council did not immediately reply to a request for comment.
Mr Waltz was blamed for accidentally adding the editor of The Atlantic magazine to a private thread describing details of an imminent US bombing campaign in Yemen. The Atlantic reported on the mishap.
At a subsequent US cabinet meeting with Mr Waltz in the room, Mr Trump expressed his preference for holding such conversations in a secure setting with lead walls, a clear sign of his displeasure. But he and others in the White House expressed confidence in Mr Waltz at the time.
However, the Signal controversy was not the only mark against Mr Waltz.
A person familiar with the cabinet's internal dynamics said Mr Waltz was too hawkish for the war-averse Mr Trump and was seen as not effectively coordinating foreign policy among a variety of agencies, a key role for the national security adviser.
"The system isn't running properly," under Mr Waltz, said the source, who spoke on condition of anonymity.
Mr Wong is an Asia expert who was a State Department official focused on North Korea during Mr Trump's first term.
The national security adviser is a powerful role but one that does not require Senate confirmation.
