Virginia Democratic Rep. Gerry Connolly, a member of the House Oversight Committee, wants White House acting chief of staff Mick Mulvaney to testify about the president’s phone call with Ukrainian President Volodymyr Zelensky.

During a 40-minute press conference Thursday, Mulvaney told reporters that $400 million in aid to the Ukraine was held up in part because of allegations related to the Democratic National Committee server and the 2016 election.