– Sen. Al Franken said Thursday that Attorney General Jeff Sessions must resign if he lied under oath about contacts with a Russian government official.

It was in response to questions from Franken in January, during Senate Judiciary Committee confirmation hearings, that Sessions said he was not aware of any contacts between the campaign of then-Republican candidate Donald Trump and the Russian government. The Washington Post reported late Wednesday that Sessions, then a U.S. senator from Alabama and a top adviser to Trump's campaign, had conversations in July and September with Russian Ambassador Sergey Kislyak.

"We now know that statement not to be true, and if it is determined that you lied under oath to the committee and the American people, it is your responsibility to resign," Franken said in a letter to Sessions.

Earlier Thursday, Franken and fellow Minnesota Democratic Sen. Amy Klobuchar demanded that Sessions recuse himself from the FBI probe into Russia's interference in last November's election. Sessions did so later in the day, as some Republicans joined Democrats in making the demand.

Sessions said at a news conference Thursday that he did not recall whether he discussed Trump or the presidential election with Kislyak. He said he would recuse himself from any investigations into aspects of the presidential campaign because he served as an adviser to Trump.

During Sessions' two days of hearings before he was confirmed as attorney general, Franken pushed him on his connections and communications with Russia.

"If there is any evidence that anyone affiliated with the Trump campaign communicated with the Russian government in the course of this campaign, what will you do?" Franken said.

"Senator Franken, I'm not aware of any of those activities. I have been called a surrogate at a time or two in that campaign and I did not have communications with the Russians and I'm unable to comment on it," Sessions responded.

Sessions said at his news conference Thursday that he was "taken aback" by Franken's question. "I should have slowed down and said I did meet one Russian official a couple times. That would be the ambassador," he said.

Klobuchar, also a member of the Judiciary Committee, asked Sessions a Russian-connected question during his confirmation hearings as well. On Thursday, she said she believed an independent prosecutor must be appointed to look at all contacts between Trump's campaign and Russia.

Klobuchar introduced legislation in early January with four other senators to create an independent commission, similar to the group of nonpartisan experts who investigated 9/11, to probe Russia's hacking in the 2016 election. Intelligence officials have said Russia hacked into e-mail servers at the Democratic National Committee, in hopes of swaying the election. Klobuchar pointed out that Sessions' September meeting with the ambassador took place three days after former President Obama said he would not roll back Russian sanctions.

"This resembles news that broke just a few weeks ago that Michael Flynn contacted the Russian ambassador on the same day the U.S. expanded sanctions on Russia," Klobuchar said. "There is nothing less at stake here than the preservation of our democracy. The American people deserve answers."

Flynn, who had been Trump's national security adviser, resigned in February after those revelations surfaced.