Washington(CNN) National security adviser Robert O'Brien says there was "absolutely" no retaliation against Lt. Col. Alexander Vindman and his twin brother, who were removed from their White House jobs last week in fallout from President Donald Trump's impeachment acquittal.
"Number one," O'Brien said, speaking to the Atlantic Council on Tuesday night, "they weren't fired."
The comments come just days after Trump did, in fact, fire Vindman and US ambassador to the European Union Gordon Sondland -- both key impeachment witnesses -- along with Vindman's twin, Lt. Col. Yevgeny Vindman, a National Security Council attorney.
And earlier Tuesday, the President told reporters in the Oval Office that he had sent Alexander Vindman back to the Pentagon and said, when asked, it was up to the military to decide whether Vindman should face disciplinary action.
"We sent him on his way to a much different location and the military can handle him any way they want," he said.
"It's up to them," he said if the military should decide on a punishment. "That's going to be up to the military. We'll have to see. But if you look at what happened, I mean they're going to, certainly, I would imagine, take a look at that."
"I obviously wasn't happy with the job he did," Trump said.
The President also said there would be more departures from the White House.
"Oh, sure. Oh, sure," he said. "Absolutely. There always are."
An adviser to Trump had said the firings of the major impeachment witnesses was meant to send a message that siding against the President will not be tolerated. "Flushing out the pipes," the adviser told CNN. "It was necessary."
On Wednesday, Defense Secretary Mark Esper declined to comment on whether he supported some sort of additional review of Vindman by the Pentagon.
"I have not seen that news," Esper told reporters traveling with him in Brussels. "I'm not going to add any more to what I have already said. I would just refer your questions at this point to the United States Army."
There is "no Army investigation" into Vindman, a US defense official with knowledge of the matter told CNN later on Wednesday.
The dismissals appeared to be retribution for Vindman's and Sondland's explosive testimony in the House impeachment probe last fall, which was done under subpoena. The duo, who gave some of the most damning testimony to House impeachment investigators during the public hearings, became targets for Trump's supporters.
Vindman was pushed out of his role months earlier than expected, according to a statement from his attorney. He had not been slated to leave until July, but had been telling colleagues in recent weeks he would likely leave soon.
Yevgeny Vindman was fired, "suddenly and with no explanation, despite over two decades of loyal service to this country," according to his lawyer, David Pressman.
However, O'Brien held Tuesday night that "none of the detailees at the NSC are fired."
"Folks might think it feels that way, and, look, it's great to work at the White House, and everybody wants to work at the White House, but there will come a time for all of us who work at the White House, including me, that (we) will leave the White House."
Both brothers were "reassigned" shortly after the impeachment trial concluded and were escorted out of the White House, which O'Brien called "standard procedure."
"Folks who have worked at the White House know this: Your last day you lose your badge, and someone walks you out to the gate," he said, "and that happens when you're at the White House as a visitor -- you have an escort who escorts you out."
"People aren't kind of free range in the White House, and if you don't have a badge to open the gate, someone has to let the Secret Service know and they let you out. So I just wouldn't read anything into that."
O'Brien then went further, saying the United States is "not some banana republic."
"We are not a country where a group of lieutenant colonels can get together and dictate what the policy of the United States is," he said. Pressed on whether he was alleging that was what had happened in the case of the Vindmans, O'Brien denied that he was.
"I'm just saying we're not that country, so the President is entitled to a staff that he has confidence in," he said. "I can absolutely tell you they were not retaliated against."
Amid uncertain futures, other witnesses in the impeachment investigation have already left the administration or distanced themselves from the White House by moving into roles at different agencies.
CNN's Kaitlan Collins, Kristen Holmes, Katelyn Polantz, Barbara Starr, Gloria Borger, Kevin Liptak, Jim Acosta and Devan Cole contributed to this report.