U.S. Sen. Cory Gardner remains unconvinced that Attorney General Jeff Sessions needs to recuse himself from the investigation into Russia’s interference in the 2016 election, despite new details and mounting pressure for Sessions to step aside.

Gardner told NPR in an interview Thursday morning that he needs more information about Sessions’ conversations with a Russian ambassador during the presidential campaign, when the former Alabama senator served as a top supporter for Donald Trump.

“I think we need to understand exactly what role, if any, he will have in the investigation,” said Gardner, a Yuma Republican. “I have full confidence in the FBI carrying out … a full and independent investigation.”

The remarks echo what Gardner said a day earlier in a virtual town hall with 10,000 people. But the new details pushed some of his GOP colleagues in Washington to join Democrats in a call for Sessions to remove himself from the Justice Department investigation.

Early Thursday, House Majority Leader Kevin McCarthy and Rep. Jason Chaffetz, the chairman of the House Oversight Committee, suggested Sessions should recuse himself.

The issue is even splitting Republicans in Colorado’s delegation. U.S. Rep. Mike Coffman, R-Aurora, said Sessions “made a grave omission” by not disclosing his meetings during his confirmation hearings.

He said it “would be more than prudent for him to recuse himself from any Russian inquiry, and I would encourage him to fully disclose any and all foreign contacts he had during the course of the campaign.”

Colorado’s Democratic U.S. Sen. Michael Bennet issued a statement shortly after Gardner’s interview aired that called on Sessions to recuse himself and appoint an independent prosecutor to investigate Russia’s actions.

“The relevant congressional committees should also include the attorney general’s communications within the scope of their investigations. The integrity of our democratic institutions is at stake, and the American people deserve the truth,” Bennet said in a statement issued by his office.

Bennet’s stance is still less strident than other Democratic lawmakers, who are calling on Sessions to resign because he told the Senate at his confirmation hearings that he never had communications with the Russians.

U.S. Rep. Diana DeGette, D-Denver, joined the demands for Sessions to resign. “If these revelations are true, he has perjured himself,” she said in a statement. “In any case, given what we now know, the attorney general should resign immediately or be removed.”

In the NPR interview, Gardner sidestepped questions about Sessions’ confirmation hearing testimony and the need for an independent prosecutor.

“I think we have to understand what exactly happened and I hope that Attorney General Sessions will come forward and outline exactly what the conversation was, talk about the substance of the meeting and help us understand why it wasn’t brought up before the committee,” Gardner said.

“There could be a reason that this was not connected to the campaign, but there are questions on whether it was,” he added, suggesting that senators often meet with ambassadors. “Let’s just have full and open transparency and just get to the bottom of it.”

Other members of Colorado’s congressional delegation did not issue immediate public statements on the issue.