WASHINGTON (AP) — A senior Defense Department official who oversees Ukraine policy is answering questions behind closed doors as part of the House impeachment inquiry into President Donald Trump.

Laura Cooper arrived Wednesday morning on Capitol Hill to appear before the House panels conducting the investigation.

Her testimony comes a day after a top U.S. diplomat testified that he was told Trump withheld military aid to Ukraine unless the country's president went public with a promise to investigate Democrats.

More than two dozen Republican House members held a news conference outside the secure room in the Capitol where the deposition with Cooper was taking place.

They decried the depositions behind closed doors and said Americans should be able to read the transcripts of any interviews being conducted as part of impeachment.