The Republican National Committee has been preparing talking points ahead of the hearing, which will be aired live on multiple TV stations.
Click for more from The New York Times. Sessions reportedly told Comey that he could not guarantee Trump wouldn't continue to attempt to speak to him one-on-one.
The FBI declined to comment to the Times for its story.
Trump's White House and its allies are crafting a strategy aimed at undermining Comey's credibility.
Current and former law enforcement officials told the Times, Comey spoke directly with Sessions about the inappropriate nature of his conversation with Trump, but did not go into specifics about Trump's request.
In a January dinner meeting, the president asked Comey to pledge loyalty to him but the director demurred, according to these associates, former colleagues of Comey.
Separately, The Washington Post reported Tuesday that Director of National Intelligence Dan Coats told associates that Trump had asked him in March if he could intervene with Comey to get the Federal Bureau of Investigation to back off the Flynn angle in its counter-intelligence probe of alleged links between Russian officials and the Trump campaign.
Comey will testify before the Senate Intelligence Committee, which is probing Russian meddling in last year's USA election, as well as any ties between Moscow and Trump's inner circle.
Calls for the assignment of an independent investigator to lead the Russian Federation investigations grew and on May 17, former FBI Director Robert Mueller was named as special counsel to oversee the FBI's investigation. Since then, Trump and Comey allies have traded competing narratives about their interactions.
Later, Sens. Chuck Grassley (R-IA) and Dianne Feinstein (D-CA) during an executive meeting of the Senate Judiciary Committee would confirm Trump's assertion.
Olson is a particularly heavy hitter, having won the Bush v. Gore Supreme Court decision that resulted in an election victory for President George W. Bush in 2000. "I greatly appreciate you informing me, on three separate occasions, that I am not under investigation". As important as that hearing was, the stakes - and the buildup - to Thursday's appearance are even bigger.
"He's become more famous than me", he said before giving him a handshake and a hug. "I will be curious to see whether and how he tries to lay a foundation for possible obstruction of justice". Such assurances would be improper, CNN quoted its sources as saying Comey would testify.
"This is a moment in history to say that the attack on the justice system stops here", she said. Among those stalwart internet warriors: President Donald Trump. "That phrase raises a lot of questions in my mind", she said. "It's not happened in my experience", Comey said.
As Trump embarked on the second-half of his first foreign trip, senior White House officials began crafting plans to create a war room-like structure to get a grip on the incessant salvo of Russia-related blockbusters.
Brian Hale, a DNI spokesman, declined to comment on whether Trump asked Coats to intervene with Comey regarding the Flynn investigation.
The Senate intelligence panel also issued its first subpoena in its Russian Federation investigation, demanding documents from Flynn.