Lt. Col. Alexander Vindman said he now identifies as a "Never Trumper" following his official retirement from the military.
In a preview clip from his interview with NBC News released on Monday, Vindman -- a key witness in the impeachment trial of President Trump over the Ukraine scandal -- was asked about whether he is a "Never Trumper," something the president and his supporters have repeatedly labeled the lieutenant coronel as.
"I joined the president's team. I joined this administration, well into this administration, with the hopes of being able to do my job, with the hopes of being able to advance national security interests," Vindman told NBC Nightly News anchor Lester Holt. "I could say I'm now a Never Trumper. I was not a Never Trumper before. I was non-partisan."
Vindman explained his evolution to Holt.
"Regardless of the administration, I would just do the best that I could to advance national security interests, but I think as the president attacked and politicized me directly, in taking a sober view of where this president is taking this country, the divisions, the catering to our adversaries, the undermining of our national security interests that I'm absolutely a Never Trumper," Vindman said.
Vindman was an important witness for Democrats during the House impeachment inquiry. He raised concerns over Trump’s July 25 phone call with Ukrainian leader Volodymyr Zelensky, in which the president pressed Ukraine to launch an investigation into Joe Biden, now the presumptive Democratic presidential nominee, and his son, Hunter.
Vindman was fired in February from the National Security Council and escorted off the White House grounds two days after the Senate acquitted Trump in his impeachment trial. His twin brother, Lt. Col. Yevgeny Vindman, was also ousted from the NSC at the same time.
Vindman served for 21 years in the military, but retired because "it has been made clear that his future within the institution he has dutifully served will forever be limited," David Pressman, Vindman's lawyer, said.
Fox News' Marisa Schultz contributed to this report.