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 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."

Darrell Issa, R-Calif., who chaired the Oversight Committee before Chaffetz, said Issa said Thursday “The news breaking overnight reaffirms what I called for in an interview last Friday, that we need an independent review by a credible third party and that Attorney General Sessions should recuse himself from any investigation into Russia. We need a clear-eyed view of what the Russians actually did so that all Americans can have faith in our institutions.“

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."

Sessions was asked directly during his confirmation hearings whether he had had any contact with Russian officials while serving as an adviser to then-candidate Donald Trump, and he said that he had not.

Some Democrats were calling on Sessions to resign from office, while others were asking only that he recuse himself from any investigation involving Russia and Trump.

"After lying under oath to Congress about his own communications with the Russians, the Attorney General must resign," said House Minority Leader Nancy Pelosi, D-Calif., referring to Sessions' testimony before the Senate Judiciary Committee during his confirmation hearing. "Sessions is not fit to serve as the top law enforcement officer of our country and must resign. There must be an independent, bipartisan, outside commission to investigate the Trump political, personal and financial connections to the Russians."

Senate Minority Leader Chuck Schumer, D-N.Y., agreed. "Attorney General Sessions had weeks to correct the record that he made before the Judiciary Committee," Schumer said at a press conference Thursday. "But he let the record stand. There cannot be even the scintilla of doubt of the impartiality and fairness of the attorney general, the top law enforcement official of the land...The Department of Justice should be above approach. For the good of the country, Attorney General Sessions should resign."

Sen. Ron Wyden, D-Ore., a member of the Senate Intelligence Committee, 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.

But Sen. Roy Blunt, R-Mo., a member of the Senate Intelligence Committee, expressed support for both Sessions and the committee's own investigation. "It would have been very normal for Sessions, as a senator, to have talked to the Russian ambassador without discussing the election." Blunt said "I take him at his word" that he never spoke to Russian officials about the election.

Blunt added that the Intelligence Committee "is the best place to determine the facts regarding Russian involvement in our elections."