Former Special Counsel Robert Mueller said he was “not familiar” with Fusion GPS — the firm whose opposition research included allegations of President Trump's connections to Russia in the run-up to Mueller’s two-year investigation — during his Capitol Hill testimony on Wednesday.

During Mueller's highly anticipated appearance before the House Judiciary Committee, Rep. Steve Chabot, R-Ohio, asked the ex-special counsel about a section of his report that referenced a heavily scrutinized meeting at Trump Tower in June 2016 with members of the Trump campaign and Russian attorney Natalia Veselnitskaya -- and asked about related research for Fusion GPS by ex-British intelligence officer Christopher Steele.

MUELLER REFUSES TO DISCUSS RUSSIA PROBE ORIGINS, STEELE DOSSIER IN TESTIMONY

“When discussing the June 2016 Trump Tower meeting, you reference ‘the firm that produced the Steele reporting.’ The name of that firm was Fusion GPS. Is that correct?” Chabot asked.

Mueller asked for the page number the congressman was referring to, and fumbled through his more than 400-page report.

“Page 103. That’s correct- Volume II. When you talk about the firm that produced the Steele reporting, the name of the firm that produced that was Fusion GPS. Is that correct?”

“I am not familiar with—with that, I—,” Mueller replied.

“It was. It’s not a trick question. It was Fusion GPS,” Chabot said.

Steele authored and compiled information for the controversial and unverified anti-Trump dossier on behalf of Fusion GPS — the firm that was hired to conduct opposition research funded by the Democratic National Committee and the Hillary Clinton campaign through law firm Perkins Coie.

The dossier “formed an essential part” of the Foreign Intelligence Surveillance Act (FISA) warrants approved to surveil then-Trump campaign associate Carter Page, according to a House GOP memo alleging government surveillance abuse during 2016.

Mueller’s report references “the firm” on Page 103 — noting that President Trump’s legal team suggested that the meeting with Veselnitskaya, former Trump campaign chairman Paul Manafort, Trump’s eldest son Donald Trump Jr., and Trump son-in-law Jared Kushner, “might have been a setup by individuals working with the firm that produced the Steele reporting.”

Fox News reported in 2017 that co-founder of Fusion GPS Glenn Simpson met with Veselnitskaya before and after the meeting at Trump Tower.

Republicans have been asking questions about the Steele dossier and the origins of the Russia investigation for months. Attorney General Bill Barr has appointed U.S. Attorney from Connecticut John Durham to probe “all intelligence collection activities” related to the Trump campaign during the 2016 presidential election. Barr assigned Durham to also conduct the inquiry into alleged misconduct and alleged improper government surveillance on the Trump campaign, as well as whether Democrats were the ones who improperly coordinated with foreign actors.

Republicans on both the House Judiciary Committee and the House Intelligence Committee planned to question Mueller on the origins of the first Russia investigation at the FBI during the summer of 2016 — but Mueller said he would not respond to those questions.

“It is unusual for a prosecutor to testify about a criminal investigation and, given my role as a prosecutor, there are reasons why my testimony will be limited,” Mueller said Wednesday, noting that his public testimony could influence “ongoing matters.”

“I am unable to answer questions about the FBI’s initial opening of the counterintelligence investigation,” Mueller continued, adding he would be unable to answer questions on “matters relating to the Steele dossier.”

“Those matters are subject to review and any questions on that should be directed to the FBI or the Department of Justice,” Mueller said, referring in part to the dossier.

His comments came within minutes of being sworn in as a witness, in an apparent attempt to tamp down Republican lawmakers’ questions on the matters.