House Speaker Nancy Pelosi warned the president not to intimidate the whistleblower, as the president continued to call for the anonymous person to be exposed.
House Republicans want the anonymous wistleblower to appear in-person, but they have not responded to an offer to have the unnamed individual answer written questions under oath.
An offer has been made to the House Intelligence Committee to open a direct channel between the whistleblower and Republicans as long as the questions do not compromise the individual's identity.
Former White House aide Fiona Hill told impeachment investigators on Monday that she and former Trump adviser John Bolton were troubled by actions by the president's private lawyer.
Attorney Mark Zaid, who is also part of the initial whistleblower's legal team, tells NPR that a new whistleblower has talked to the inspector general of the intelligence community.
