House impeachment investigators ordered Mick Mulvaney, the acting White House chief of staff, to testify Friday as part of their inquiry.
Despite the subpoena, Mulvaney is still expected to not show up for the closed-door deposition.
Lawmakers issued the subpoena two days after they initially invited Mulvaney to testify on Capitol Hill.
The chairmen of the House Intelligence, Oversight and Foreign Affairs committees told Mulvaney in a letter that they believe he has "substantial first-hand knowledge and information relevant to the House's impeachment inquiry."
During a White House briefing last month, Mulvaney admitted President Trump withheld military aid to pressure Ukraine into opening investigations into his political rivals. Mulvaney later walked back the comment, saying "there was absolutely no quid pro quo."
The White House has directed administration officials not to participate in the impeachment investigation, which President Trump has characterized as another "witch hunt."
The House committees scheduled more than a dozen witnesses to testify this week as part of their inquiry. But as of Friday morning, only two have shown up.
Additional reporting from Newsy affiliate CNN.
