The comments, which occurred in the Oval Office during a ceremony to finalize a bill creating new job assistance programs for veterans, came five days after the officer — Lt. Col. Alexander Vindman — was dismissed from his post on the National Security Council.
The Ukraine-born infantry officer made headlines in October after he testified before the House Intelligence Committee about Trump's phone call with the Ukrainian president, expressing concerns that Trump attempted to use the call to start a foreign investigation into his political rival, former Vice President Joe Biden.
Vindman was scheduled to rotate out of the NSC post this summer. White House officials characterized his early move not as retribution for his testimony, but as downsizing bureaucracy and restructuring the office.
A day later, Trump attacked Vindman as having "problems with judgement" and suggested he was a substandard worker. On Tuesday, he said Vindman was dismissed for misrepresenting the call in his testimony.
"The military can handle him any way they want," Trump said. "We'll find out what happens. But I wasn't happy with the job he did."
When asked if that meant some type of discipline, Trump said "they certainly have to take a look at that."
Last fall, Defense Secretary Mark Esper said Vindman had no reason to fear retribution for testifying before Congress — which had subpoenaed him — in the impeachment inquiry, and that he would be shielded by department whistleblower protections.
He added Vindman or any other whistleblower "shouldn't have any fear of retaliation."
Trump also accused Vindman of leaking sensitive information from his White House post. In a statement over the weekend, Vindman's attorney, David Pressman, called those allegations "obviously false statements" by the president.
"While the most powerful man in the world continues his campaign of intimidation, while too many entrusted with political office continue to remain silent, Lt. Col. Vindman continues his service to our country as a decorated, active duty member of our military," Pressman said.
Army officials have not released any information on Vindman's future posts or responsibilities. They have confirmed that Vindman's twin brother, Lt. Col. Yevgeny Vindman, was also ousted from his role as a judge advocate assigned to the NSC last week.