FILE PHOTO: U.S. House Intelligence Committee Chair Adam Schiff (D-CA) talks to reporters after testimony from Acting Director of National Intelligence (DNI) Joseph Maguire about the handling of the whistleblower complaint on Capitol Hill in Washington, U.S., September 26, 2019. REUTERS/Leah Millis/File Photo

WASHINGTON (Reuters) - U.S. House Intelligence Committee Chairman Adam Schiff, a top Democrat in the inquiry into a whistleblower complaint that could ultimately cost President Donald Trump the White House, warned Secretary of State Mike Pompeo not to stop diplomatic officials from testifying before congressional committees.

“We are deeply concerned about Secretary Pompeo’s effort now to potentially interfere with witnesses whose testimony is needed before our committee, many of whom are mentioned in the whistleblower complaint,” Schiff said at a press conference. His remarks come one day after Pompeo pushed back on House Democrats’ efforts to take depositions from State Department officials, accusing the lawmakers of bullying and intimidation.

“And we want to make it abundantly clear that any effort by the secretary, by the president or anyone else to interfere with the congress’ ability to call before it relevant witnesses will be considered obstruction of the lawful functions of congress,” Schiff said.

Obstruction charges can be used to impeach a president under the U.S. Constitution.