Asked about the scope of his inquiry, Grassley said it would look at Comey and the Russian Federation investigation, saying the intelligence committee has a "pretty narrow" jurisdiction.
North Carolina Republican Richard Burr and Virginia Democrat Mark Warner aren't providing any other details regarding the meeting.
President Donald Trump lashed out Thursday at the investigators driving the Russian Federation investigation as "very bad and conflicted people", responding angrily to reports that the special counsel is looking into whether Trump obstructed justice.
Rosenstein testified that he is the only one who has the authority to fire Mueller, who was appointed following the May 9 ousting of James Comey as Federal Bureau of Investigation director, and that he had seen no good cause to do so.
218529218525218525Claiming vindication, Trump answers Comey testimonyPresident Trump spoke out publicly a day after former FBI Director James Comey Friday testified that to protect against lies by Mr. Trump, he had taken detailed notes, some of which he leaked in hopes of prompting the naming of a special counsel.More news: Australia v Bangladesh Match Preview
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"You (Grassley) and I agree that these matters - termination of the FBI Director and any efforts to interfere with the independence of ongoing investigations - fall squarely in the jurisdiction of the Judiciary Committee", Feinstein wrote in the letter.
So she says in a letter to the committee's chairman, GOP Sen.
The Washington Post reported late Wednesday that Mueller was seeking interviews with three Trump administration officials who weren't involved in Trump's campaign: Dan Coats, the director of national intelligence; Michael Rogers, the head of the National Security Agency; and Richard Ledgett, the former NSA deputy director. But Jim Comey testified that he was the person that first requested a private meeting with the president on January 6. Dianne Feinstein of California.
In a February meeting, Comey said, Trump told Sessions and other administration officials to leave the room before asking him to drop a probe into former National Security Adviser Michael Flynn's contacts with Russian Federation.
"I would have a queasy feeling, too, though, to be candid with you", Feinstein told CNN host Brianna Keilar on "State of the Union." . Grassley also wants the investigation to look at Obama attorney general Loretta Lynch and whether she influenced the Clinton email scandal investigation.
"We also were aware of facts that I can't discuss in an open setting that would make his continued engagement in a Russia-related investigation problematic", Comey said.