Democratic congressional leaders on Wednesday urged the FBI and Justice Department to include more top lawmakers in a highly sensitive meeting about the Russia investigation set for later this week.

In a letter to Deputy Attorney General Rod Rosenstein and FBI Director Christopher Wray, the top House and Senate Democrats Nancy Pelosi and Chuck Schumer pushed them to add Democratic and Republican leaders to the meeting. They asked for the so-called Gang of Eight — the bipartisan leaders of both chambers of Congress as well as the top ranking Republican and Democrat on the House and Senate Intelligence Committees — to be included.

As of now, House Intelligence Committee Chairman Rep. Devin Nunes and House Oversight Committee Chairman Rep. Trey Gowdy, both Republicans, are the only lawmakers set to attend Thursday. While President Donald Trump will not join in the meeting, Wray, Director of National Intelligence Dan Coats, and Principal Associate Deputy Attorney General Ed O'Callaghan are expected to attend, the White House said Wednesday.

The gathering comes as Trump and his allies in Congress allege government abuse of power in the probe into whether the Trump campaign colluded with the Russian government during the 2016 election. Recently, Trump has fixated on the possible use of an informant to gather information on his campaign.

In their letter, Pelosi and Schumer write that "this meeting is improper in its proposed form and would set a damaging precedent for your institutions and the rule of law."

"We urge you to reconsider holding this meeting," the Democrats add. "However, if you have determined in your best judgment that Justice Department participation in the meeting is the only way to prevent this situation from devolving into an outright constitutional crisis, then we believe you must insist on the only appropriate mechanism for highly sensitive briefings that might implicate intelligence sources and methods — a bipartisan Gang of Eight briefing that involves congressional leadership from both chambers."

Speaking to reporters Wednesday, Trump said he wants "total transparency" about the investigation and added that he thinks Democrats want information out in the open, too.

Criticism of the meeting has also come from the Republican side of Capitol Hill. In a tweet Wednesday, Sen. Jeff Flake, R-Ariz., said "this is not right."

"Briefings like this should be bipartisan," he wrote.

Flake tweet

It is unclear whether law enforcement agencies will include the Gang of Eight leaders in the meeting. The FBI declined to comment. The Justice Department and spokespeople for Nunes and Gowdy did not have immediate responses to the Democrats' requests.

On Wednesday, White House press secretary Sarah Huckabee Sanders said Democrats will not attend because "my understanding is they haven't been the ones requesting this information."

The documents are expected to include information about the FBI source used in the investigation and the intelligence the person provided.