Sessions faces questions about his contacts with Russia's ambassador to the USA during the presidential campaign. And he can expect questions about his involvement in Comey's May 9 firing, the circumstances surrounding his decision to recuse himself from the FBI's investigation, and whether any of his actions - such as interviewing candidates for the FBI director position or meeting with Trump about Comey - violated his recusal pledge.
Attorney General Jeff Sessions could be at the center of two controversies in the Trump administration: whether Donald Trump's campaign colluded with Russian Federation to help Trump win and whether the president obstructed justice.
Media reports last week said Mr Sessions had offered to resign because of tensions with the president.
On May 17, Robert Mueller was appointed by the Justice Department as Special Counsel to oversee the Russian Federation investigation.
Spicer, the spokesman, 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".
He also recused himself from his own agency's Russian Federation probe.
The appearance comes after Comey reportedly told committee members Sessions had an unreported meeting with Russian officials. This will be the first time Sessions has testified since he formally recused himself from the Department of Justice's investigation into potential collusion between the Trump campaign and the Russian government.
"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. Preet Bharara told ABC's "This Week" that Trump was trying to "cultivate some kind of relationship" with him when he called him twice before the inauguration to "shoot the breeze".
On "Fox & Friends" Monday, Conway noted Comey's testimony that Loretta Lynch, as President Barack Obama's attorney general, directed him to describe the FBI probe into Hillary Clinton's email practices as a "matter" and to avoid calling it an investigation. Senators from both sides want to know why Sessions was involved in the Federal Bureau of Investigation director's firing, reports CBS News' Nancy Cordes.
But the top justice official agreed to the open hearing after Democrats on the committee pressed for it.
But, in contrast to Comey's detailed account, it is unclear to what extent Sessions will be willing or able to answer the committee's questions, with the possibility that he might invoke executive privilege on some key matters.
Lankford said Sessions' testimony Tuesday will help flesh out the truth of Comey's allegations, including Sessions' presence at the White House in February when Trump asked to speak to Comey alone.
The White House has rejected any collusion with Russian Federation, which has denied meddling in the U.S. election. Ron Wyden, D-Ore., a member of the committee, said on Sunday. Comey was leading that probe.
While several committee members, including Dianne Feinstein, D-Calif., Susan Collins, R-Maine, and Angus King, I-Maine had voiced support for a public hearing, other members have complained that doing so will inevitably lead to a brick wall, where Sessions will say he can not discuss certain matters in public.
