President Donald Trump on Thursday announced his nomination of Rep. Michael Waltz to serve as the next U.S. Ambassador to the United Nations, while Secretary of State Marco Rubio will assume the additional role of interim national security adviser.

“I am pleased to announce that I will be nominating Mike Waltz to be the next United States Ambassador to the United Nations,” Trump wrote on his conservative social media platform. “From his time in uniform, in Congress, and as my National Security Advisor, Mike has always put America’s interests first. I’m confident he’ll bring that same commitment to the United Nations.”

Trump also confirmed that Rubio will temporarily take on national security duties while continuing to lead the State Department. “Together, we will continue to fight tirelessly to Make America, and the World, SAFE AGAIN,” the president said.

Sources earlier told ABC News that Waltz’s departure from his national security role had been expected, following a recent controversy in which he mistakenly added a journalist to a secure Signal group chat discussing a classified U.S. military operation targeting Houthi rebels in Yemen.

The shake-up comes amid heightened foreign policy tensions and appears aimed at reinforcing Trump’s core diplomatic and national security team ahead of a series of expected international summits.

Following President Trump’s announcement, Michael Waltz responded on X, writing, “I’m deeply honored to continue my service to President Trump and our great nation.”

Secretary of State Marco Rubio was attending a National Prayer Event at the White House when the news broke. He was seen speaking on the phone while standing in the colonnade, at times conferring with White House Deputy Chief of Staff Stephen Miller.

At the State Department, spokesperson Tammy Bruce appeared caught off guard when asked about Rubio’s new role during a press briefing. As reporters questioned whether Rubio would consider the position, news of Trump’s appointment was posted in real time.

“It is clear that I just heard this from you,” Bruce said, reacting on the spot. She praised Rubio as “a man who, as I think you all know, has worn several hats from day one” and called him “someone who is well known by the president.”

Bruce added that while the move wasn’t “entirely surprising,” it reflected the intensity and speed of Trump’s second term. “These last 100 days, it’s like hanging onto a freaking bullet train,” she said.