But Comey wouldn't say exactly what in open session.
There is a way that Sessions could skirt around having to directly answer these questions, however.
Why this is a big deal: Sessions is a Trump ally, and he appears to be caught between the president and his promise to run the Justice Department in an apolitical way. There had been some question as to whether the hearing would be open to the public, but the Justice Department said Monday he requested it be so because he "believes it is important for the American people to hear the truth directly from him".
But Sessions will be able to corroborate, or not, details of Comey's version of events before and after the encounter, during which, Comey says, Trump all but directed him to back off an investigation into retired Army Lt. Gen. Michael Flynn, who until hours earlier had been Trump's national security adviser.
A number of members are concerned Sessions may be attempting to avoid testifying in public by scrapping his previously scheduled Senate and House Appropriations appearances this week, where he was expected to be grilled on issues related to the federal investigation into Russia's efforts to influence the U.S. election, several sources say. Sen.
Besides Trump's son-in-law Jared Kushner, Sessions is the highest-profile member of Trump's campaign and administration who we know met with Russians during the 2016 campaign and didn't disclose it. Sessions didn't disclose those meetings when he was asked, under oath, in his confirmation hearing.
Spokesman Spicer declined to say then that Sessions enjoyed Trump's confidence, though spokeswoman Sarah Huckabee Sanders said later in the week that the president had confidence "in all of his Cabinet".
The announcement caps the drama that started over the weekend when Sessions canceled two appearances Tuesday, citing former Comey's blistering testimony last week.
Though we may not learn a lot about the Russian Federation investigation, we will be able to better assess Sessions' survival by the end of the day. Multiple sources confirmed that the president was disappointed with the attorney general's recusal - a decision he only learned about minutes before it was announced in March. As he did so, he defended himself against allegations of improper contacts, saying, "Let me be clear: I never had meetings with Russian operatives or Russian intermediaries about the Trump campaign".
Comey's dramatic testimony drew invective from his former boss on Twitter, with Trump dismissing him as a leaker on Friday and a coward on Sunday.
Sessions is the first of six high-level officials Comey said were asked to leave the room. "I kind of got - his body language gave me the sense like, 'What am I going to do?'". The White House has denied any collusion with Moscow.
But officials said Sessions's relationship with Trump has been strained since the attorney general recused himself from the Russian Federation probe in March.
Attorney General Jeff Sessions attends a Cabinet meeting with. Officials said that Sessions at one point offered to resign as his relationship with the president became increasingly tense.