He will also likely be asked if he knows of any ties between anyone in Trump's campaign who may have coordinated with the Russians, and if there is any suggestion of obstruction of justice by the president following the firing of national security adviser Michael Flynn. She described Comey's testimony as "candid" and "thorough" and said she would support a subpoena of any tapes if needed.
Hawaii's Attorney General Doug Chin says a ruling that upholds the blocking of President Donald Trump's travel ban shows why the country has three branches of government.
The White House, the Justice Department and the Federal Bureau of Investigation did not respond immediately to requests for comment.
The appearance before the Senate intelligence committee comes one week after former FBI Director Comey cryptically told lawmakers the bureau had expected Sessions to recuse himself weeks before he did from an investigation into contacts between Trump campaign associates and Russian Federation during the 2016 election. Charles Schumer of NY, the Senate's top Democrat.
"I don't understand why the president just doesn't clear this matter up once and for all", said Sen.
But officials said Sessions's relationship with Trump has been strained since the attorney general recused himself from the Russian Federation probe in March.
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.
Stephen Gillers, a professor of law at New York University, said Sessions has not answered why he played a role in Comey's firing given that he had recused himself from the Russian Federation investigation. Sessions reportedly threatened to resign as tensions with Trump grew.
"The Attorney General has requested that this hearing be public", Justice Department spokeswoman Sarah Isgur Flores said in a statement.
"If he was recused, as he says he was, he should not have participated in the Comey firing", Gillers said. "I was honestly concerned that he might lie about the nature of our meeting, and so I thought it really important to document", the ex-FBI director testified.
Trump's aides have dodged questions about whether conversations relevant to the Russian Federation investigation have been recorded, and so has the president. The Justice Department has denied that, saying Sessions stressed to Comey the need to be careful about following appropriate policies. On Saturday, he wrote the chairmen of both committees and said he was sending his deputy attorney general to testify in his place. They also emphasized Comey's admission that he arranged to have contents of his memos leaked to the news media.