WASHINGTON — Top intelligence and law enforcement officials will meet on Thursday with Republican congressional leaders to share highly classified information related to an F.B.I. informant who contacted members of the Trump campaign in the early days of the Russia investigation, a White House official said on Tuesday.
But even those few details prompted confusion around Washington, with a Justice Department official refusing to confirm the White House’s announced guest list and Democrats on Capitol Hill complaining they were not invited.
The meeting promised to be a flash point in the standoff pitting President Trump and his congressional allies against his own administration’s top law enforcement officials.
At the root of the dispute is a subpoena by Representative Devin Nunes, Republican of California and the House Intelligence Committee chairman, for all documents referencing or related to the informant, an American academic who met on behalf of the F.B.I. with Trump associates.
Top law enforcement and intelligence officials initially refused the request, saying disclosure would put the source at risk and endanger key intelligence partnerships. Mr. Nunes, who has pushed for greater and greater access to sensitive case files, did not like that answer and threatened to hold the attorney general and his deputy in contempt of Congress.
That was before Mr. Trump waded into the fray over the weekend, publicly ordering the Justice Department to investigate the F.B.I.’s use of the informant and all but siding with Mr. Nunes and his allies.
His demand prompted an outcry over whether he was assailing the longstanding independence of the Justice Department to gain information about the investigation into his campaign’s possible ties to Russia’s election interference. Democrats have long accused Mr. Nunes, a close ally of the president, of exploiting his oversight role to undermine the inquiry.
The White House stepped in, ostensibly to mediate the dispute. The Thursday meeting will include Christopher A. Wray, the director of the F.B.I.; Dan Coats, the director of national intelligence; and Edward O’Callaghan, a top Justice Department official, according to Sarah Huckabee Sanders, the White House press secretary.
Absent from her list was Rod J. Rosenstein, the deputy attorney general who is overseeing the Russia investigation and who has tangled extensively with Mr. Nunes. It was unclear why he was not included, and Justice Department officials would not confirm who planned to attend the meeting.
It likewise remained unclear how much information the department would hand over, in what form and whether it would satisfy Mr. Nunes — who has indicated that nothing short of the department opening its files would satisfy him.
Ms. Sanders said no one from the White House staff would attend the meeting — one relief for Democrats who feared that John F. Kelly, the White House chief of staff, would attend and could report back to Mr. Trump on key information about the investigation into his campaign.
But on Capitol Hill, the arrangement still prompted only confusion and complaints from Democrats, who had yet to hear whether they would receive an invitation to an identical briefing.
Ms. Sanders said, “To my knowledge, the Democrats have not requested that information, so I would refer you back to them on why they would consider themselves randomly invited to see something they’ve never asked to.”
Representative Adam B. Schiff of California, the top Democrat on the Intelligence Committee, said he would prefer to sit in alongside Mr. Nunes, but that he had been told by department officials that the chairman refused to allow it.
“There is a mechanism to brief the Congress on the most sensitive information that might implicate sources and methods. It’s called the gang of eight — and they ought to use it,” Mr. Schiff said in an interview.
He added: “I don’t think any of us have any idea what the White House is doing.” Mr. Schiff said he still expected to be invited, noting that lawmakers have a standing agreement that Democratic leadership is granted access to the same intelligence as Republicans.
When asked to comment on the meeting by reporters, Mr. Nunes said he did not discuss committee business with reporters. Then, he suggested the reporters watch his Sunday television appearances, where he frequently discusses committee business.
Mr. Trump, for his part, continued to gripe about the informant on Tuesday to reporters in the Oval Office.
“A lot of people are saying they had spies in my campaign. If they had spies in my campaign, that would be a disgrace to this country,” Mr. Trump said. “That would be one of the biggest insults that anyone has ever seen.”
No evidence has emerged that the F.B.I. acted improperly in using an informant in the early days of the Russia investigation. Current and former officials have said that agents were reluctant to take aggressive steps in the middle of a presidential campaign, lest the existence of the inquiry become public. They sent the informant to tip them off to speak to two campaign advisers who had suspicious contacts linked to Russia during the campaign.
When asked on Tuesday whether he had confidence in Mr. Rosenstein, a miffed Mr. Trump declined to answer.
“He doesn’t want to hear these questions, if you don’t mind,” he said, gesturing to his guest, President Moon Jae-in of South Korea.