U.S. National Security Advisor Mike Waltz is set to leave his post, President Donald Trump announced on Thursday, marking the first high-profile cabinet reshuffle of the second Trump administration. Waltz’s deputy, Alex Wong, is also reportedly leaving.

In a post on Truth Social, Trump said that Secretary of State Marco Rubio would serve as acting national security advisor, in addition to his current duties. Trump also announced that he will nominate Waltz to be ambassador to the United Nations, which unlike the position of national security advisor requires Senate confirmation.

“From his time in uniform on the battlefield, in Congress and, as my National Security Advisor, Mike Waltz has worked hard to put our Nation’s Interests first. I know he will do the same in his new role,” Trump said.

GOP Rep. Elise Stefanik of New York was initially tapped for the U.N. ambassador role, but Trump withdrew her nomination over concerns about the Republican Party’s narrow majority in the House.

The news of Waltz’s departure as national security advisor comes a little over a month after he emerged at the center of the Signalgate scandal. In March, Waltz accidentally included a journalist in a Signal group chat with other top officials in which sensitive information on impending U.S. strikes in Yemen was discussed.

Waltz’s future in the new administration was immediately called into question as a result of Signalgate, despite the White House downplaying the significance of the controversy and maintaining that no classified information was shared—an assertion that national security veterans have treated with a great deal of skepticism. Signalgate remains a thorn in the administration’s side, with Defense Secretary Pete Hegseth also facing ongoing scrutiny. The scandal is likely to come up in any confirmation hearing involving Waltz’s future.

Though Trump expressed confidence in Waltz amid the initial fallout from the Signalgate controversy, his influence in the White House rapidly dwindled in the aftermath.

The national security advisor’s ouster comes just weeks after Trump fired several staffers from the National Security Council (NSC) following a meeting with Laura Loomer, a far-right activist and conspiracy theorist, over allegations of disloyalty.

Loomer appeared to celebrate and take credit for the dismissals of Waltz and Wong on Thursday, as news reports suggested Waltz would be fired, and before Trump announced his nomination as ambassador to the United Nations. “Hopefully, the rest of the people who were set to be fired but were given promotions at the NSC under Waltz also depart,” Loomer said in a post on X. Loomer has publicly pushed for Wong to be fired, while attacking him and his wife over their Chinese heritage. On Thursday, Loomer posted “SCALP” on X while resharing an older post in which she criticized Wong.

In addition to facing blame for Signalgate, Trump advisors and allies also reportedly viewed Waltz as too hawkish on Russia and Iran at a time when the president is pursuing a peace agreement to end the Russia-Ukraine war as well as a new nuclear deal with Tehran. But it’s widely suspected that Loomer’s growing influence over Trump is largely to blame here.

“Unfortunately, I think this is the handiwork of Laura Loomer and her fringe conspiracists,” former State Department spokesperson Ned Price told Foreign Policy regarding Waltz being ousted, adding that “very little” in the Trump administration is purely about ideology.

“Yes, Waltz had been out of step on key issues: Ukraine, Russia, and Iran among them. But I suspect he’s out today because Loomer and her fellow travelers wanted him out. It should be of great concern to all Americans that she and her ilk have such sway over this White House, even its national security apparatus,” Price added.

Loomer did not immediately respond to a request for comment.

National security advisors are typically among the most influential officials in the White House. Under former President Joe Biden, for example, National Security Advisor Jake Sullivan held significant sway over U.S. foreign policy and was consistently one of the most public-facing officials in the administration.

But in Trump’s second term, the role of national security advisor has so far been downgraded, as he hollows out the NSC and takes an unorthodox approach to the presidency and especially foreign affairs—favoring inexperienced loyalists and outsiders, such as Steve Witkoff, over seasoned national security veterans or career officials.