Mueller investigating President Trump for obstruction of justice: Wash

"I don't think the only options are you have to spill the beans on anything you've said with the president of the United States, or you have to invoke Executive Privilege, particularly when you're appearing voluntarily as all these witnesses do", said Cotton.

Sessions is expected to face sharp questions from his former Senate colleagues about his role in FBI Director James Comey's firing, his Russian contacts during the campaign and his decision to step aside from the investigation involving Moscow and the Trump campaign.

In his testimony on Tuesday, Sessions addressed media reports that he may have had a third previously undisclosed meeting with Kislyak at Washington's Mayflower Hotel a year ago. Sessions said he was in an Oval Office meeting in February with Comey and Trump when the president said he wanted to speak to Comey privately - and he acknowledged that Comey came to talk to him the next day about the meeting. Comey's decision to announce a year ago that Clinton would not be prosecuted over her emails was a "usurpation" of the Justice Department's authority, Sessions said.

And he repeatedly refused to reveal whether he had spoken to the President regarding Mr James Comey's handling of the probe into Russian election meddling - which the former Federal Bureau of Investigation (FBI) director believes to be the reason he was sacked.

The Justice Department ultimately agreed to a Tuesday public hearing in an attempt to show there's nothing to hide and nothing controversial about Sessions' interactions with Russian officials, officials said.

A screengrab of U.S. Attorney General Jeff Sessions on Tuesday. "What are they?" Wyden had asked.

"We are talking about an attack on our democratic institutions and stonewalling of any kind is unacceptable ... there is no legal basis for this stonewalling", Oregon Senator Ron Wyden said.

"We also were aware of facts that I can't discuss in an open setting that would make his continued engagement in a Russia-related investigation problematic", Comey said. Sessions told Wyden he did not appreciate the "secret innuendo being leaked out there about me".

The dossier, containing salacious and false allegations that Russian Federation has compromised Trump, has been "largely discredited", Sessions testified.

Sessions has said that those meetings were in his capacity as a member of the Senate Armed Services Committee. Sessions added his own letter to that effect, and both documents were sent to Trump, who then fired Comey later on the same day, May 9.

Deputy Attorney General Rod Rosenstein, who appointed Mueller, hinted broadly that the special counsel investigation could be looking at Trump during a House committee hearing on Tuesday. "I have confidence in Mr. Mueller", he said.

In his Tuesday testimony, Sessions was unable to provide any more context to this question: Did Trump fire Comey because of, or in response to, the FBI director's refusal to "let go" of the investigation into Trump's national security adviser, Mike Flynn?

It is not clear whether the White House could use executive privilege to try to block them from speaking to the investigators.

Sessions hedged nearly all of his answers about whether/when he met with Russians, or why he was involved in firing Comey, or how he feels about the president's decisions, with: "I don't recall" or "I believe so" or "maybe".

The meeting was one of 25 meetings with foreign ambassadors Sessions held in 2016, Sessions said.

"If Trump and his associates have done something improper, you've got to investigate that as well", Stewart said.