This one has been simmering since confirmation hearings for Sessions earlier this year, as some Democrats have all but accused Sessions of perjury; Republicans say it's nothing close to that.
During former FBI Director James Comey's public testimony before the intelligence committee last week, he highlighted Sessions's role in the Trump team's connections with Russian Federation and hinted at more that could not be revealed in a public setting.
Last week, Comey told senators that the Federal Bureau of Investigation was looking into whether Sessions had a third undisclosed conversation with Kislyak at the Mayflower Hotel in April, 2016, when the two were both at a Trump campaign event.
Since then, lawmakers have raised questions about a possible third meeting at a Washington hotel, though the Justice Department has said that did not happen.
Sen. Brian Schatz, D-Hawaii, said he was troubled that Sessions wouldn't appear before the appropriations panel and that the apparent reason was "he does not want to discuss the scope of his recusal from the investigation regarding the 2016 presidential campaign as well as his significant interactions with Russian officials".
"He believes it is important for the American people to hear the truth directly from him", a spokesperson said.
The Justice Department issued a statement saying that Sessions had requested the panel be open just minutes before the committee announced it.
The hearing will bring sharp questioning for Sessions and likely some uncomfortable moments from the Trump administration.
Questioned by Sen. Ron Wyden (D-OR), Former FBI Director James Comey dropped a hint about some kind of information with regards to Attorney General Sessions and the Russian Federation investigation, which Comey was convinced would lead to Sessions recusing himself from the Russian Federation probe. The Justice Department has said that while Sessions was there, for a speech by Trump, there were no meetings or private encounters. "To get into a hypothetical at this point would be premature".
"It's great to be here and celebrate this group", Mr. Sessions said at the president's first full Cabinet meeting.
If Washington was in the throes of Comey fever last week, Sessions' public appearance won't generate anywhere near that kind of attention.
Comey told the intelligence committee in a closed session that Sessions may have had a third, undisclosed interaction with Russia's ambassador to the USA, according to people familiar with the briefing.
Trump has been coy about whether any recordings exist of his private conversations with Comey, who was sacked by the president in May.
Sessions has said the meetings were not relevant to the question asked of him.
"We must not enable the attorney general to avoid public scrutiny by our committee out of concern that such testimony would be embarrassing".
Sen. Richard Burr, R-N.C., chairman of the Senate Intelligence Committee, and Sen.
"[Sources] are telling me Trump has been very angry with Jeff Sessions for recusing himself in the Russian Federation investigation to begin with, lots of profane conversations and yelling". If President Donald Trump is also keeping recordings of his conversations, any controversy over those will have begun with a tweet. Though Trump did not accept it, he has expressed unhappiness with the justice department, which Sessions heads, in a series of posts on Twitter for watering down his travel ban. In March, Sessions chose to do the smart thing-albeit only after his meetings with Kislyak were leaked to the press-by recusing himself from all matters related to the ongoing investigation into Russian election interference.