President Trump says he will nominate his national security advisor, Michael Waltz, to serve as America’s next ambassador to the United Nations. The president says Secretary Rubio will take over as the acting national security advisor in the meantime. 

Mr. Waltz has faced criticism for weeks for his mistaken addition of a journalist to a Signal group chat where war plans were discussed. He was also viewed by some as being out of step with Mr. Trump’s “America First” foreign policy agenda, given his hawkish stances on certain issues like keeping forces in Afghanistan and potentially launching a military operation against Iran. 

“I am pleased to announce that I will be nominating Mike Waltz to be the next United States Ambassador to the United Nations. 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,” Mr. Trump wrote on Truth Social on Thursday. 

“In the interim, Secretary of State Marco Rubio will serve as National Security Advisor, while continuing his strong leadership at the State Department. Together, we will continue to fight tirelessly to Make America, and the World, SAFE AGAIN,” the president declared. 

Mr. Rubio will now concurrently be serving as secretary of state, national security advisor, administrator of the U.S. Agency for International Development, and the archivist of the United States. 

The position of ambassador to the UN became vacant earlier this month when Congresswoman Elise Stefanik was forced to withdraw from the process due to Republican concerns about narrow majorities in the House coming at the same time that Speaker Johnson was trying to pass Mr. Trump’s “one big beautiful bill.” 

Ms. Stefanik won her seat in upstate New York last year by 20 points, though two special elections in Florida to fill the seats of Mr. Waltz and Congressman Matt Gaetz saw Democrats improve their margins by 15 points. Mr. Trump said he was concerned that a similar swing to the left in Ms. Stefanik’s district could hand Democrats the seat. 

It was first reported by journalist Mark Halperin on Thursday that Mr. Waltz was likely to be removed from his post in the West Wing in the coming hours or days. Until the president’s announcement, the White House offered no public defense of Mr. Waltz even though he had been doing interviews for the administration as late as Thursday morning. 

In March, Mr. Waltz received unyielding criticism after he accidentally added journalist Jeffrey Goldberg to a Signal group chat in which Secretary Hegseth shared timelines for American attacks on Houthi assets in Yemen. Mr. Trump stood by him at the time. 

Conservative activist Laura Loomer — who has been denounced by Congresswoman Marjorie Taylor Greene for past racist statements — had been advising the president about firing Mr. Waltz and his deputy Alex Wong, whom she believed were too hawkish for the administration. Mr. Wong was previously the top national security and foreign policy advisor to Senator Cotton. 

When news reports began circulating that Messrs. Waltz and Wong would leave their White House posts, Ms. Loomer wrote of Mr. Wong: “SCALP.”