Angeli was reportedly hanging out for Trump to pardon him during his final days in office, and when it didn't happen he said he felt "duped".
"He regrets very, very much having not just been duped by the President, but by being in a position where he allowed that duping to put him in a position to make decisions he should not have made," his lawyer Albert Watkins told KSDK news outlet at the time.
Over the weekend, Watkins told Metro UK that Angeli had turned against the former President and would offer to testify during the impeachment trial.
He said Angeli was willing to take to the stand when the trial kicks off on February 8 because he "felt like he was betrayed by the President".