United States President Donald Trump has removed Mike Waltz from his position as national security adviser, replacing him temporarily with Secretary of State Marco Rubio, while nominating Waltz to serve as the next US ambassador to the United Nations.

The move marks the first high-profile departure from the White House in Trump’s second term and comes amid a controversy involving the accidental inclusion of a journalist in a private Signal chat discussing sensitive military operations.

In a post on his social media platform, Truth Social, the president thanked Waltz for his service. “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,” Trump wrote. “I know he will do the same in his new role.”

The announcement comes just weeks after Waltz admitted to mistakenly adding The Atlantic’s editor-in-chief, Jeffrey Goldberg, to a Signal chat that included discussions on potential military strikes against Yemen’s Houthi rebels. Participants in the chat reportedly included Secretary of State Marco Rubio, Defence Secretary Pete Hegseth, and Waltz’s deputy, Alex Wong.

Multiple sources familiar with internal White House deliberations told US media outlets that the decision to remove Waltz stemmed from the incident, as well as broader concerns over his handling of National Security Council staffing. Despite these concerns, Trump is believed to still hold Waltz in high regard, offering him what observers have described as a “soft landing” through the prestigious UN post.

However, some officials who spoke to the BBC on condition of anonymity expressed doubt over Waltz’s ability to be confirmed by the Senate. They suggested that nominating him to a post requiring congressional approval was a strategic way to sideline him without a direct dismissal.

Waltz, a former Florida congressman and US Army veteran, issued a brief statement on social media, saying, “I’m deeply honoured to continue my service to President Trump and our great nation.”

The episode has reignited concerns over the handling of classified information within Trump’s national security team. At a congressional hearing in March, lawmakers questioned several officials reportedly involved in the Signal conversation, including the CIA director and the director of national intelligence. The fate of Alex Wong remains uncertain following the shake-up.

Meanwhile, Rubio’s surprise appointment as interim national security adviser has drawn comparisons to Henry Kissinger, who held both the state and national security portfolios under President Nixon. Senior officials at the State Department were reportedly blindsided by the decision.

Rubio, a prominent figure in Trump’s second-term cabinet, now also oversees the United States Agency for International Development (USAID) and the National Archives, both of which have seen diminished capacity under the current administration.

While the UN ambassador post remains vacant following the withdrawal of Elise Stefanik’s nomination earlier this year, speculation over a permanent successor has intensified. Among the names being floated are Steve Witkoff, a real estate developer and Trump confidant currently serving as a special envoy to the Middle East, and Ric Grenell, a former ambassador with longstanding ties to the Trump administration.

In a television interview on Thursday evening, Vice President JD Vance rejected claims that Waltz was dismissed, insisting instead that he had been promoted. “I like Mike. I think he’s a great guy. He’s got the trust of both me and the president,” Vance told Fox News.

However, the controversy continues to attract public scrutiny. During a recent cabinet meeting, a Reuters photographer captured an image of Waltz on his phone, engaged in a Signal chat with a contact saved as “JD Vance.” The visible portion of the message read: “I have confirmation from my counterpart it’s turned off. He is going to be here.”

Minnesota Governor and former Democratic vice-presidential candidate Tim Walz appeared to poke fun at the incident, posting on X, “Mike Waltz has left the chat.”

Trump, who cycled through four national security advisers during his first term, faces renewed questions about the stability and discipline of his national security apparatus as he enters the middle stretch of his second term.