Asked about a pending announcement of his foreign policy team, Trump listed Papadopoulos as one of five advisers.
Writing to the Russian contact a week before the Republican National Convention, Papadopoulos proposed a meeting for August or September in the United Kingdom that would include "my national chairman and maybe one other foreign policy adviser" and members of Putin's office and Russia's foreign ministry.
On March 31, Trump's campaign released a picture of the candidate meeting with his foreign policy team, and Papadopoulos is shown at the table.
The revelations revived questions about Sessions's credibility. The Minnesota Democrat said the latest disclosure suggests that the American people "cannot trust your word".
It is a crime to lie under oath to Congress. Sessions says that his answers were truthful because his meetings with Kislyak weren't specifically about the campaign.
Though he refused to say whether he discussed with Trump Comey's involvement in the Russian Federation investigation, he did say that the president had asked him and Rosenstein for their recommendations about what to do with Comey. If Sessions were pushed out, it would give Trump the chance to appoint a new attorney general - who would have the authority to fire Mueller and take over the Russian Federation probe.
Sources familiar with the emails tell ABC News the "campaign supervisor" was Sam Clovis.
In a statement released earlier this week, Clovis said Papadopoulos "was acting on his own and that the campaign had a strict rule against traveling overseas and claiming to speak on behalf of the campaign", Bloomberg News reported.
Court papers unsealed Monday revealed an indictment against Trump's former campaign chairman, Paul Manafort, and a guilty plea by another adviser, who admitted to lying to the Federal Bureau of Investigation about meetings with Russian intermediaries.
White House staffers who have been called to meet with Mueller have usually kept the President's legal team in the loop.
The campaign officials aren't named in the document, but Paul Manafort was campaign chairman at the time, and Clovis was in place as national co-chairman. "As far as Sessions seemed to be concerned, when he shut down this idea of Papadopoulos engaging with Russian Federation, that was the end of it and he moved the meeting along to other issues".
That's a hard claim to swallow, since Papadopoulos was in regular contact with top campaign officials and met with a number of foreign officials as a Trump surrogate.
Sessions replied: "I'm not aware of any of those activities".
The email exchange could be significant in investigations into Russian election meddling.
Senator Lindsey Graham, a Republican member of the Judiciary Committee, said it makes sense to ask Sessions to clarify the chain of events and how he reconciles it with his testimony before the committee.
He added: "I certainly think it's a legitimate area of inquiry" for lawmakers to pursue.
"Jeff Sessions was the head of the national security operation" in Trump's campaign, Senator Richard Blumenthal of CT, a member of the Judiciary Committee, said in an interview.