House Intelligence Committee Chairman Adam B. Schiff said Sunday that his panel has reached an agreement to secure testimony from the anonymous whistleblower whose detailed complaint launched an impeachment investigation last week into President Trump.

Schiff (D-Calif.) said he expected the Intelligence Committee to hear from the whistleblower “very soon” pending a security clearance from acting director of national intelligence Joseph Maguire.

“We’ll get the unfiltered testimony of that whistleblower,” Schiff said on ABC News’s “This Week,” noting that Maguire said in a hearing Thursday that he would allow the whistleblower to testify privately without constraints.

The whistleblower kicked off the impeachment saga that came to a head with Speaker Nancy Pelosi’s announcement Tuesday of an “official impeachment inquiry.” In that nine-page Aug. 12 complaint filed with the inspector general of the intelligence community, the whistleblower accused Trump of “using the power of his office to solicit interference from a foreign country in the 2020 U.S. election” — in particular, through a July 25 phone call with Ukrainian President Volodymyr Zelensky.

On Sept. 29, President Trump's personal lawyer and other Republicans criticized a whistleblower complaint, while Democrats insisted on its gravity. (The Washington Post)

Numerous Republicans have attacked the whistleblower complaint as “hearsay,” noting that the information contained in it came from secondhand sources.

Schiff said Sunday that does not make the complaint less credible because key allegations in it were confirmed by a rough transcript of the Trump-Zelensky call as well as other sources.

Late-night hosts had a lot to say about the Sept. 26 release of the whistleblower complaint against President Trump. (Drea Cornejo/The Washington Post)

“This whistleblower has already been substantially corroborated, which suggests that other information that he or she provides in that complaint likewise may be subject to corroboration,” he said. “So do not dismiss both the professionalism of this whistleblower, and — and this is what we would expect of someone who comes out of the intelligence community.”

Schiff declined to say whether he knew of other whistleblowers who have come forward in recent days but encouraged any officials with information about the allegations to step up.

“We are dependent on people of good conscience coming forward, particularly now, given that we have such an unscrupulous president,” he said.