“The Whistleblower gave false information & dealt with corrupt politician Schiff,” Trump wrote on Twitter, referring to House Intelligence Chairman Adam Schiff (D-Calif.), one of the leaders of the impeachment probe.

“He must be brought forward to testify,” the president continued. “Written answers not acceptable!”

Attorney Mark Zaid, the whistleblower’s attorney, said Sunday that he had contacted Rep. Devin Nunes (R-Calif.), the ranking member of the House Intelligence Committee, to offer Republican members of that panel the opportunity to submit written questions to his client’s legal team.

The whistleblower would respond to those queries under oath and penalty of perjury, Zaid said — attempting to undercut Republican complaints regarding a lack of transparency in the Democratic-led impeachment process and to blunt skepticism toward the unknown intelligence official’s allegations.