A trio of influential Senate Republicans, cut out of a high-stakes meeting this week on classified information about a confidential FBI source who aided an investigation into Trump campaign advisers, is asking the White House to be allowed to review the material.

Senate Judiciary Committee Chairman Charles E. Grassley (Iowa), Sen. Lindsey O. Graham (S.C.) and Senate Majority Whip John Cornyn (Tex.) made the request in a letter obtained by The Washington Post. In it, the senators stress their “interest in attending such a meeting and in support of providing Congress with documents necessary to conduct oversight of these issues.”

“On Sunday, Deputy Attorney General [Rod J.] Rosenstein stated: ‘If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action.’ We agree,” the three Republican senators wrote to Rosenstein and White House Chief of Staff John F. Kelly. 

The letter was dated Tuesday. Grassley has been spearheading his own committee investigation into Russian interference into the 2016 campaign. Graham and Cornyn are also members of the Judiciary Committee. 

Just two congressional Republicans — House Intelligence Committee Chairman Devin Nunes (Calif.) and Rep. Trey Gowdy (S.C.) — have been invited to the meeting, the White House said Tuesday. Administration officials attending include FBI Director Christopher A. Wray, Director of National Intelligence Daniel Coats and Principal Associate Deputy Attorney General Ed O’Callaghan.

Although Kelly arranged the meeting, no White House officials will attend, press secretary Sarah Huckabee Sanders said.

In a separate letter sent Wednesday to Rosenstein and Wray, Senate Minority Leader Charles E. Schumer (D-N.Y.) and House Minority Leader Nancy Pelosi (D-Calif.) urged the officials to abandon plans for the meeting. If the meeting is held, the Democrats asked that it be opened up to a bipartisan group of eight lawmakers.

“This meeting is completely improper in its proposed form and would set a damaging precedent for your institutions and the rule of law,” Schumer and Pelosi said. “We can think of no legitimate oversight justification for the ex parte dissemination — at the direction of the president — of investigative information to the president’s staunchest defenders in Congress and, ultimately, to the president’s legal defense team.”

The White House did not immediately respond to a request for comment Wednesday on whether the GOP senators will be allowed into the meeting. But Rosenstein has assured Grassley in the past that his committee would have access to the same information that has been provided to the House Intelligence Committee in its probe. Republicans on the panel have concluded the investigation, without Democrats’ input.

The meeting is part of the long-running battle between President Trump and his conservative allies in Congress against the Justice Department over the FBI’s use of the confidential source — former University of Cambridge professor Stefan A. Halper, who was in contact with at least three Trump advisers during the presidential campaign. 

Democrats have lambasted the administration for excluding them from the Thursday meeting, with Rep. Adam B. Schiff (Calif.), the ranking Democrat on the Intelligence Committee, describing the move as a “serious abuse of power.” But Sanders noted that Democrats had not made similar requests for the information. 

The material is so sensitive that the leaders of the Senate Intelligence Committee, Sens. Richard Burr (R-N.C.) and Mark R. Warner (D-Va.), have declined previous offers to be briefed about the source because of concerns that the classified information could leak from Capitol Hill. 

Rep. Thomas J. Rooney (R-Fla.), a senior member of the House Intelligence Committee, also acknowledged Tuesday that there is reason to worry that some members may disclose the information they receive. 

“You do have to be careful with regard to people that might potentially leak for political reasons,” he said.

Karoun Demirjian and John Wagner contributed to this report.