Defense Secretary Mark Esper Mark EsperTop admiral: 'No condition' where US should conduct nuclear test 'at this time' Overnight Defense: Trump hosts Israel, UAE, Bahrain for historic signing l Air Force reveals it secretly built and flew new fighter jet l Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Oldest living US World War II veteran turns 111 MORE on Friday said the Pentagon protects its service members from retribution, following reports that President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE may oust the top White House expert on Ukraine after he testified during House impeachment hearings.

“We protect all of our persons, service members, from retribution or anything like that. We’ve already addressed that in policy and other means,” Esper told reporters at the Pentagon during a press conference with his Colombian counterpart.

Reports emerged early Friday that the White House would remove Lt. Col. Alexander Vindman, a National Security Council (NSC) aide, from his role and that he would be reassigned to a position within the Defense Department.

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Trump later in the day addressed the reports, telling journalists that he was "not happy" with Vindman but would not say if he would have the aide removed.

“Well, I'm not happy with him. You think I'm supposed to be happy with him? I'm not. They'll make that decision. You'll be hearing. They'll make a decision,” he told reporters at the White House before departing for North Carolina.

Vindman in November testified before the House impeachment committees during their inquiry that he believed Trump improperly demanded that Ukrainian President Volodymyr Zelensky investigate former Vice President Joe Biden and his son Hunter Biden in order for Kyiv to receive military aid.

That demand, which came during a July phone call between the two leaders, was at the center of the House impeachment probe.

Vindman also later defended career officials who testified in the inquiry.

The Republican-controlled Senate voted this week to acquit Trump on abuse of power and obstruction of Congress charges.

When asked if Vindman would be welcomed back to the Pentagon, Esper replied: “We welcome back all of our service members wherever they served, to any assignment they are given.”