CNN  — 

Lt. Col. Alexander Vindman, a key witness in President Donald Trump’s impeachment inquiry, has told colleagues he expects to leave the White House’s National Security Council in the coming weeks to return to the Defense Department, a source tells CNN.

Vindman said his departure from the council could come as soon as this month, the source said. That would be well ahead of the scheduled end of his time at the White House, which was originally slated to last until July. Vindman was appointed to his post in July 2018 and was asked to stay for two years.

The source did not say whether Vindman’s departure was voluntary or at the behest of the White House, though aides inside the West Wing had speculated it could come soon as the impeachment trial was over.

Trump on Friday would not directly answer whether he wanted Vindman out of the White House, only telling reporters on the South Lawn, “Well, I’m not happy with him.”

“You think I’m supposed to be happy with him? I’m not,” Trump said, adding, “They’ll make that decision. You’ll be hearing. They’ll make a decision.”

The President later provided hints of where he stood, retweeting Republicans on Twitter who called for Vindman to be removed.

Trump has continued to fume about Vindman’s presence at the National Security Council since he testified publicly in November, according to people familiar with the matter. Vindman’s duties were significantly curtailed after he testified – as were his those of his brother, an attorney for the council, according to sources familiar with the situation.

Late last year, CNN reported that the President’s aides explored moving some impeachment witnesses who were at the National Security Council out of the White House. Such a move could be seen as retaliation for participating in the inquiry, though the council’s head has argued that he wants to seriously reduce the size of the council.

In November, Defense Secretary Mark Esper told reporters that Vindman “shouldn’t have any fear of retaliation” for coming forward.

Esper reiterated that sentiment Friday, saying that the Pentagon would “protect all of our persons, servicemembers from retribution” when asked about Vindman.

House Speaker Nancy Pelosi told reporters Friday that she’s “stunned” by the reports of Vindman’s expected departure from his job.

“That’s such a shame. What a patriotic person,” Pelosi said on Capitol Hill.

News of Vindman’s likely departure follows another witness, Jennifer Williams, who left Vice President Mike Pence’s office two months ahead of schedule.

CNN’s Veronica Stracqualursi, Allison Malloy, Jeremy Herb, Michael Conte and Jamie Crawford contributed to this report.