WASHINGTON — Top congressional Republicans began calling Thursday for Attorney General Jeff Sessions to recuse himself from any investigation of the Trump campaign's contacts with Russia after revelations that Sessions met with the Russian ambassador to the United States while advising the Trump campaign but did not disclose those meetings during his confirmation hearing.

Ohio Republican Sen. Rob Portman said Thursday, “Jeff Sessions is a former colleague and a friend, but I think it would be best for him and for the country to recuse himself from the DOJ Russia probe.”

Rep. Jason Chaffetz, R-Utah, chairman of the House Oversight and Government Reform Committee, tweeted Thursday that "AG Sessions should clarify his testimony and recuse himself."

House Majority Leader Kevin McCarthy of California said in an appearance on MSNBC that the attorney general should recuse himself in order to maintain "the trust of the American people." But later Thursday morning, he appeared on Fox & Friends to walk back his comments. "I'm not calling on him to recuse himself," McCarthy said. He explained that he was merely repeating Sessions' position that the attorney general should recuse himself if and when that becomes appropriate.

Sessions on Thursday told NBC News "I have not met with any Russians at any time to discuss any political campaign." He also repeated his prior statements that he will recuse himself from an investigation if it becomes necessary at some point.

Sessions, who was a U.S. senator from Alabama and Trump campaign adviser when he met with the Russian ambassador, has denied discussing campaign-related matters with Russian officials.

"I never met with any Russian officials to discuss issues of the campaign," Sessions said in a statement released late Wednesday. "I have no idea what this allegation is about. It is false."

Sen. Ron Wyden, D-Ore., a member of the Senate Intelligence Committee, also called late Wednesday for a special counsel to be appointed since Sessions made "false statements."

"Given AG Sessions’ false statements about contacts with Russian officials, we need a special counsel to investigate Trump associates' ties to Russia," Wyden said.