Democrats must approve any requests submitted by Republicans and they are expected to reject the requests for Hunter Biden and the whistleblower to appear.
CNN has reached out to attorneys for the whistleblower and Hunter Biden for comment.
In the letter, California Rep. Devin Nunes, the top Republican on the House Intelligence Committee, bashed what he called a “sham impeachment process.” Nunes wrote that Republicans were calling the witnesses to testify in an open setting to “provide transparency to your otherwise opaque and unfair process.”
House Democrats are moving forward with their probe into allegations that Trump pushed Ukraine to investigate Joe Biden, the former vice president’s son and the 2016 election in order to help the President politically and that the White House took steps to cover it up. Trump has denied doing anything improper.
Trump has pushed an unproven accusation that then-Vice President Biden improperly tried to help his son by pressuring the Ukrainian government to fire the country’s prosecutor general. Hunter Biden served on the board of the Ukrainian natural gas company at the time.
There is no evidence of wrongdoing by either Joe or Hunter Biden in Ukraine.
The Biden presidential campaign declined to comment to CNN Saturday on the request for the former vice president’s son to testify. Joe Biden was asked Friday in New Hampshire whether he himself would testify at a Senate impeachment trial if asked — though Republicans have not yet made that request.
“Let’s focus on the problem, here,” Biden said. “The question is, did the President of the United states violate the Constitution … And did he profit from his office.” He again called on Trump to release his tax returns.
It roiled efforts to bolster a key strategic alliance after Trump enlisted his own personal attorney, Rudy Giuliani, to work outside normal diplomatic channels in an apparent effort to bolster his reelection chances.
CNN’s Jeremy Herb, Manu Raju and Marshall Cohen contributed to this report.