Mike Waltz and his deputy Alex Wong were both set to leave the White House, CBS News and others reported, while Fox News said Trump was expected to comment on the matter soon.
The 51-year-old former congressman from Florida lasted just over 100 days of Trump’s second term, which has so far been more stable in terms of personnel than his first.
Trump cycled through four national security advisors during his first presidency.
A White House official did not confirm the reports, saying they “do not want to get ahead of any announcement.”
Waltz showed no sign that he knew of his imminent departure when appearing early on Wednesday on Fox News, where he hailed the new US minerals deal with Ukraine.
“Nobody said (it) could be done. President Trump said ‘get it done’,” he said.
Saying Trump has boosted US military recruitment, he added: “This is leadership at its finest, led by our commander in chief, who loves the troops and they love him.”
Waltz was also present at Trump’s televised cabinet meeting on Wednesday.
A former special forces officer, Waltz was seen as a moderate voice in the Trump administration when he was appointed, but reportedly clashed with other officials over his hawkish stance against Russia and Iran.
Trump has pushed for Ukraine to reach a quick ceasefire deal with Russia, while reopening negotiations with Iran over its nuclear programme.
Steve Witkoff, a real estate magnate whom Trump has picked to lead US talks with both Russia and Iran, is in contention to replace Waltz, US media reported.
Waltz had been under pressure since late March, when the editor-in-chief of The Atlantic Magazine revealed he had been mistakenly added to a chat on the commercial messaging app Signal about military attacks on Yemen’s Houthi rebels.
Officials on the chat laid out the attack plan, including the timings that US warplanes would take off to bomb targets, with the first texts barely half an hour before they launched.
Despite intense media speculation that Trump would fire Waltz over the scandal, the president repeatedly offered his backing, and the national security advisor appeared to have ridden out the storm. (AFP)
