Lawyers for the whistleblower at the center of an impeachment inquiry into President Trump’s dealings with the Ukrainian president have asked if it’s possible for him to provide written testimony instead of appearing in front of Congress, a report said Thursday.

The request shows the lawyers’ concern over the whistleblower’s identity being kept secret — and if that can happen if he testifies in a closed-door congressional hearing, the Wall Street Journal reported.

“We continue to work w/both parties in House & Senate and we understand all agree that protecting whistleblower’s identity is paramount,” Mark Zaid, the lawyer who represents the anonymous whistleblower, said on Twitter in late September.

“Discussions continue to occur to coordinate & finalize logistics but no date/time has yet been set,” Zaid added.

Lawyers for the CIA officer who filed the whistleblower complaint about Trump’s phone call with Ukrainian President Volodymyr Zelensky fear his safety could be put in jeopardy if he is publicly identified, the Wall Street Journal reported.