The House Intelligence Committee opened its historic impeachment hearing to the public Wednesday with Chairman Adam Schiff warning Republicans not to reveal the identity of the whistleblower whose bombshell complaint helped launch the probe of President Donald Trump.
"We will not permit the outing of the whistleblower," Schiff said in response to questions from Republican panel members.
"If necessary, I will intervene" to prevent the identity of the whistleblower from being shared in the public hearing, the California Democrat added. "Otherwise, I want members to feel free to ask any questions they like."
The whistleblower, who has been reported as a CIA employee who had worked in the White House, raised alarms about Trump's July 25 call with Ukraine President Volodymyr Zelenskiy, which was held while a multimillion-dollar military aid package to Ukraine was being withheld without clear explanation by the Trump administration.
Trump asked Zelenskiy in that call to investigate former Vice President Joe Biden, who at the time was the front-runner in the Democratic presidential primary, and his son Hunter. Trump also requested that Zelenskiy "do us a favor though" and investigate a conspiracy theory about Ukraine's alleged interference in the 2016 election.
At the hearing, top Ukraine diplomat William Taylor and senior State Department official George Kent became the first witnesses to testify publicly, marking the next chapter of the impeachment investigation that Trump and Republicans have decried as a "sham."
Kent and Taylor previously testified behind closed doors that Trump's associates, including his personal attorney Rudy Giuliani, had been involved in the campaign to pressure Ukraine to announce the investigations Trump sought.
Schiff, who opened the hearing by laying out a timeline of Trump's efforts toward Ukraine, was interrupted early in the hearing by Rep. Elise Stefanik, R-N.Y., about the potential witnesses that Republicans had requested.
She then asked whether witnesses will be prohibited from answering GOP members' questions.
"The only times I prevented witnesses from answering questions" in prior closed-door hearings "was when it was apparent that members were seeking to out the whistleblower," Schiff responded.
"We will do everything necessary to protect the whistleblower's identity, and I'm disturbed to hear members of the committee who have in the past voiced strong support for whistleblower protections, seek to undermine those protections by outing the whistleblower," he added.
Rep. Jim Jordan, R-Ohio, an aggressive defender of Trump, then chimed in.
"You are the only member who knows who that individual is," Jordan said, referring to the whistleblower, "and your staff is the only staff of any member of Congress who has had a chance to talk with that individual. We would like that opportunity. When might that happen in this proceeding today?"
Jordan was likely making a reference to reports that the whistleblower had contacted a member of Schiff's staff for guidance before filing the complaint.
Schiff shot back: "First, as the gentlemen knows, that's a false statement. I do not know the identity of the whistleblower and I'm determined to make sure the identity is protected."
But, the chairman added, "you'll have an opportunity after the witnesses have testified to make a motion to subpoena any witness and compel a vote."
Jordan had been called onto the Intelligence Committee by House Minority Leader Kevin McCarthy as a substitute for Republican Rep. Rick Crawford, R-Ark., who has previously been critical of President Trump and is retiring at the end of his term.
— CNBC's Christina Wilkie contributed to this report.