Schiff says Pompeo trying to 'interfere with witnesses' in U.S. impeachment inquiry

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.

Trump kept up his assaults on the Democratic lawmakers leading impeachment proceedings on Wednesday, accusing Schiff of treason, as well as attacking the unidentified whistleblower who reported concerns about his behavior.

The Republican president has lashed out repeatedly at the impeachment inquiry, which was prompted by his phone call with the Ukrainian president that sought an investigation that would be damaging to a Democratic political opponent, former Vice President Joe Biden.

Trump repeatedly says he did nothing wrong in his July 25 telephone call in which he asked Ukrainian President Volodymyr Zelenskiy to investigate a domestic political rival Joe Biden, the former U.S. vice president.

He has repeatedly attacked Schiff, who is leading the impeachment inquiry.

"They should look at him for treason because he is making up the words of the president of the United States - not only the words but the meaning," Trump said.

He accused the Democrats' impeachment efforts of being groundless and politically motivated.

"They've been trying to impeach me from the day I got elected," Trump said.

He again referred to his call with the Ukrainian leader as "perfect."

During a news conference earlier on Wednesday, Democratic House Speaker Nancy Pelosi had a different message for Trump on his call: "It's not perfect. It's wrong."