President Donald Trump announced Thursday that he would nominate national security adviser Mike Waltz to serve as UN ambassador, after widespread reports that Trump planned to oust him, in the first major staff shakeup since the president took office in January.

US National Security Adviser Mike Waltz is leaving his post with the Trump adminstration, according to media reports. Waltz, who was the president's principal adviser on national security issues, has had a difficult tenure amid accusations that senior officials used insecure methods of communication to conduct government business.

Days after former National Security Adviser Mike Waltz was caught using a knock-off Signal app, a hacker broke into the system.

Then-National Security Adviser Michael Waltz participates in a TV interview at the White House on May 01, 2025 in Washington, D.C. | Photo by Andrew Harnik/ In the end, it wasn’t Signalgate that toppled Mike Waltz,