WASHINGTON — President Trump plunged on Wednesday into the simmering dispute between conservative House Republicans and the deputy attorney general, Rod J. Rosenstein, siding with the lawmakers and attacking his own Justice Department.
Mr. Trump called the legal system “rigged” in a tweet and gave voice to the complaints of a small group of congressmen who have assailed the Justice Department as slow or unresponsive to their demands to produce sensitive documents that the lawmakers say they need to conduct oversight.
“At some point I will have no choice but to use the powers granted to the Presidency and get involved!” Mr. Trump wrote. It was not immediately clear which presidential powers Mr. Trump was referring to, but he has been critical of Mr. Rosenstein, who is overseeing the special counsel investigation and, by law, is the only one who can shut down the inquiry or fire the special counsel, Robert S. Mueller III.
It is well within Mr. Trump’s presidential powers to fire Mr. Rosenstein, as he has fired other senior Justice Department officials whom he blames for the sprawling inquiry into Russia’s election interference and whether Mr. Trump obstructed the investigation itself.
Mr. Rosenstein and the small group of House Republicans who are loyal to Mr. Trump have been facing off for months, as the lawmakers have demanded greater access to documents and information related to some of the departments most politically charged cases, including the Russia inquiry. Mr. Rosenstein, aware of the threats against him, has maneuvered to try to meet those requests and reached an agreement last week with two Republicans who run the committees that conduct oversight of the Justice Department to satisfy the last of their outstanding demands.
But those efforts have not quieted two of Mr. Trump’s most loyal supporters on Capitol Hill, Representatives Mark Meadows of North Carolina and Jim Jordan of Ohio. In an unusual show of defiance of their committee chairman, they have insisted the agreement is not good enough and that they need access to an unredacted version of an August 2017 memo outlining the scope of Mr. Mueller’s investigation.
Democrats fear that the Republican requests — many of which call on the department to ignore longstanding policy about what it shares with Congress — are meant to trap Mr. Rosenstein into either turning over information that could be used to undermine Mr. Mueller’s investigation or refusing, thereby giving Mr. Trump cover, or even cause, to fire the deputy attorney general.
Representative Jerrold Nadler of New York, the top Democrat on the Judiciary Committee, said the latest Republican efforts were “clearly trying to sabotage” the Mueller investigation and court a confrontation with Mr. Rosenstein.
“All of this noise is aimed at undermining the special counsel’s work as the investigation closes in on the president,” Mr. Nadler said in a statement. “The president’s attacks on the Department of Justice grow more paranoid by the day. The case for obstruction of justice — and the complicity of these House Republicans — grows day by day as well.”
Mr. Rosenstein, who has already given the Republican lawmakers access to hundreds of thousands of pages of documents, has made clear in recent days that he does not intend to go further.
The Justice Department wrote to Mr. Meadows and Mr. Jordan on Monday to deny them access to the document about the scope of the Russia inquiry, citing department policy against sharing information on a continuing investigation.
“The department recognizes the keen interest that Congress has in the special counsel’s investigation, but, respectfully, we must adhere to the longstanding position of the department that congressional inquiries pertaining to ongoing criminal investigations threaten the integrity of those investigations,” Stephen E. Boyd, an assistant attorney general, wrote in the letter, a copy of which was provided to The Times.
“We hope you can respect our position,” he added.
And on Tuesday, reacting to reports that Mr. Meadows had drafted articles of impeachment to use against him if needed, Mr. Rosenstein declared that the Justice Department would not be “extorted.”
“There have been people who have been making threats, privately and publicly, against me for quite some time,” he said at an event in Washington. “And I think they should understand by now, the Department of Justice is not going to be extorted.”
Mr. Meadows fired back, saying that Mr. Rosenstein was stonewalling legitimate oversight requests and calling on him to resign.
It is unusual for rank-and-file members of a committee to challenge or maneuver around their own chairmen on sensitive matters. But Mr. Jordan and Mr. Meadows, the past and current chairman of the conservative House Freedom Caucus, are known as two of the most confrontational and influential Republicans in the chamber. Mr. Meadows has also developed a close relationship with Mr. Trump.
Neither lawmaker was immediately available for comment on Wednesday.
A Justice Department official said that the department had gone as far as giving House staff temporary office space on site to review hundreds of thousands of documents previously studied by Michael Horowitz, the inspector general. The official said that dozens of lawmakers and staff members from both parties had already reviewed thousands of classified documents.
In an apparent break with both men, one of the two Republican chairmen, Representative Trey Gowdy of the Oversight Committee, said on Wednesday that he was “satisfied” that his committee and the Judiciary Committee now had the access it needed to documents relevant to an ongoing joint investigation into decisions made by the department in 2016 and 2017.
“I appreciate Rosenstein’s willingness to work with the Committees, and I have confidence in his leadership,” Mr. Gowdy said, adding that Mr. Mueller should be given “the time, the independence and the resources to conduct a thorough investigation.”
Last month, Mr. Trump said Mr. Rosenstein faced conflicts of interest and criticized him for signing a search warrant application to permit federal agents to eavesdrop on one of the president’s former campaign aides. Mr. Rosenstein assumed oversight of the investigation and appointed Mr. Mueller as special counsel after the attorney general, Jeff Sessions, recused himself last year. Mr. Trump has repeatedly attacked Mr. Sessions for his recusal.
The president has previously said he is frustrated that he is not supposed to be involved with Justice Department matters.
“I am not supposed to be involved with the F.B.I. I’m not supposed to be doing the kind of things that I would love to be doing. And I’m very frustrated by it,” Mr. Trump said in an interview last November.
The president’s threats, though vague, come at a time when he has been on the defensive after the disclosure of more than 40 questions that the special counsel would like him to answer. The questions touch on a variety of topics, including coordination with the Russians during the presidential campaign and actions Mr. Trump has taken as president and whether they were intended to derail the inquiry, undercutting the president’s repeated claims that the investigation is a “hoax.”
Charlie Savage contributed reporting.