WASHINGTON — Frustrated House members emerged from a briefing on Friday with Rod J. Rosenstein, the deputy attorney general, with few fresh insights into the firing of James B. Comey as F.B.I. director and with new doubts about the trajectory of the investigations into Russian election meddling.
Representative Seth Moulton, Democrat of Massachusetts, said there was “considerable frustration” among lawmakers as Mr. Rosenstein declined to answer many questions about the events leading to the abrupt termination of Mr. Comey last week.
“This renewed my confidence that we should not have confidence in this administration,” Mr. Moulton said. Asked whether that included Mr. Rosenstein, he said, “I don’t think he did a lot to bolster our confidence in him.”
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Mr. Rosenstein also offered little clarity about how the congressional inquiries — which, like the F.B.I. investigation now led by a special counsel, Robert S. Mueller III, are examining the possibility of collusion between President Trump’s associates and Russian officials — would remain separate. The fact that Mr. Mueller’s inquiry is focused on possible crimes is almost certain to limit the cooperation of potential subjects of the investigation who might otherwise testify before Congress or share documents.
“Congress is going to want to look over the shoulder of this investigation,” said Representative Darrell Issa of California, a Republican who was an aggressive chairman of the House Oversight Committee during the Obama administration. “The executive branch will always try to limit that for fear it will contaminate potential criminal investigations, or leaks.”
“I don’t expect this to be any different,” he added.
Representative Jackie Speier of California, a Democrat on the House Intelligence Committee, said Mr. Rosenstein made it clear that Mr. Mueller would have “carte blanche authority,” but he also reassured lawmakers that he understood the role of Congress.
“I think he’s very respectful of the role that the Congress is playing in doing its investigation,” she said, “and the separate and distinct role that the Department of Justice is pursuing.”
Mr. Mueller’s appointment on Wednesday by Mr. Rosenstein posed a challenge for Democrats, who were simultaneously heartened by the installment of a respected former F.B.I. director and prosecutor to lead an investigation that they fear has been tarnished by Mr. Trump’s interference, and concerned about the possibility of losing their grip on the information coming out of their own investigations.
The New York Times has reported that Mr. Trump asked Mr. Comey for his “loyalty” during a private dinner and requested he drop the investigation into Michael T. Flynn, his former national security adviser, who is under scrutiny regarding his ties to Russia and Turkey.