Senate Democrats on Wednesday called for Attorney General Jeff Sessions to recuse himself from any executive branch investigation into possible ties between the Trump administration and Russia.

Minority Leader Chuck Schumer, D-N.Y., said Sessions should not be involved because of potential conflicts of interest and because of Justice Department regulations that prohibit individuals with political ties to the subjects of an investigation from leading it. President Donald Trump nominated Sessions for the attorney general’s post and the senator was one of his earliest and staunchest backers in Congress.

But Republicans continued to brush off demands from Democrats for a Watergate-style probe, insisting investigations underway by the House and Senate intelligence committees are adequate.

“When the FBI looks into a matter, they do so alongside prosecutors from the Justice Department,” Schumer said. “Those prosecutors should not be reporting to the first senator who endorsed Donald Trump’s campaign.”

Schumer and other Democrats spoke to reporters as Trump criticized the intelligence agencies that he oversees and the media for what he described as unfair treatment of his former national security adviser, Michael Flynn, and for “illegally leaked” information about reported contacts between his campaign aides and Russian officials.

Flynn was forced to resign Monday following reports he misled Vice President Mike Pence about contacts with a Russian diplomat. Late Tuesday, The New York Times reported that U.S. agencies had intercepted phone calls last year between Russian intelligence officials and members of Trump’s 2016 campaign team.

Sen. Roy Blunt, R-Mo., a member of the Senate Intelligence Committee, said involving other committees in the investigation will slow the inquiry down. “I think sooner is better than later,” Blunt told reporters. “And I think we can be a long way down the road in 90 days.”

Sen. John McCain of Arizona, the Republican chairman of the Senate Armed Services Committee, didn’t rule out an independent probe but said he and other lawmakers “need to find out a lot of basic information” first about Flynn’s communications and the alleged contacts involving Trump’s campaign.

“Something like this always sucks the oxygen out of the room,” McCain said. “The president’s national security adviser did not tell the vice president of the United States the truth and had to be fired. It brings up a lot of questions and those questions need to be answered. Right now, without a national security adviser and everything else that’s going on in the White House, it is dysfunctional on national security.”