WASHINGTON (Reuters) – U.S. President Donald Trump’s national security adviser Mike Waltz is being forced out of his job, four people briefed on the matter said on Thursday, in the first big shakeup of Trump’s inner circle since he took office in January.

Waltz’s deputy, Alex Wong, an Asia expert who was a State Department official focused on North Korea in Trump’s first term, is also leaving his post, two people told Reuters.

A 51-year-old former Republican lawmaker from Florida, 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 Waltz, but one option included U.S. 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.

Waltz was blamed for accidentally adding the editor of The Atlantic magazine to a private thread describing details of an imminent U.S. bombing campaign in Yemen. The Atlantic reported on the mishap.

At a subsequent Cabinet meeting with Waltz in the room, 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 Waltz at the time.

However, the Signal controversy was not the only mark against Waltz.

A person familiar with the Cabinet’s internal dynamics said Waltz was too hawkish for the war-averse 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 Waltz, said the source, who spoke on condition of anonymity.

The national security adviser is a powerful role but one that does not require Senate confirmation.

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(Reporting by Steve Holland, Erin Banco, Jeff Mason, Gram Slattery and Katharine Jackson; Editing by Colleen Jenkins and Alistair Bell)