Comey set to lay out uncomfortable relationship with Trump Sources close to the former FBI director say he merely wants to be a witness.

 -- As the countdown begins for James Comey's highly-anticipated congressional hearing Thursday, sources tell ABC News that the former FBI director will describe an uncomfortable relationship with President Trump and repeated encounters that made him uneasy.

Comey's interactions with Trump have come under intense scrutiny since his firing last month, causing some lawmakers to question whether it was related to the ongoing FBI investigation into alleged Russian meddling during the 2016 presidential election.

Among the Senate Intelligence Committee's primary inquiry will be to ask Comey about those encounters and the contemporaneous notes he reportedly took of his meetings with the president.

Senators specifically want to know if Trump sought a pledge of loyalty from Comey early on --- and if Comey was pressured to go easy on former national security adviser Michael Flynn, who was fired for misleading Trump administration officials about meetings he had had with Russia's ambassador the U.S.

At the meeting where Comey is said to have rebuffed the president's reported loyalty pledge, one source described Comey as viewing the attempt as an amateurish effort to bring him under the president's wing.

During their meetings, Comey was constantly assessing the president's motive, unsure whether Trump was doing something sinister or was someone simply used to getting his way and not versed in the protocols of Washington whereby the FBI director enjoys broad independence.

For its part, the White House has previously disputed published media accounts of the Comey and Trump meetings.

But Comey was concerned enough to make sure he was taking notes about certain meetings, especially the one in which Trump suggested he go easy on Flynn. Comey made no final conclusion about the encounter but decided to chronicle it for the future.

Two sources told ABC News that shortly after that meeting, Comey told Attorney General Jeff Sessions that he did not want to be left alone with the president, though he did not go into the specifics of why, other than he didn't think it would be appropriate protocol.

Comey wanted to simply continue the investigation and keep the president at arm's length –- not doing anything that would taint investigators' view of the president, but maintaining notes that would be there in case something dramatic happened later on.

A week after Comey was fired, Deputy Attorney General Rod Rosenstein, who was in charge of the Russia investigation after Sessions recused himself, appointed former FBI Director Robert Mueller as special counsel to oversee the probe.

ABC's sources say that Comey will not volunteer a belief that Trump committed obstruction of justice in his interactions with the former FBI director, as Comey believes that judgment is the purview of investigators and special counsel Mueller.

Rather, Comey is said to view himself merely as a witness who will answer questions about the president in a straightforward manner.

However, ABC News' sources emphasize that Comey has been reflecting on events that have happened since his firing: the president's suggestion that he was incompetent; the president openly stating in an interview that Russia was on his mind when he fired Comey; and reports that the president told the Russian ambassador to the U.S. and Russian Foreign Minister Sergey Lavrov that Comey was a "nut job" and that his firing had relieved pressure.

Comey is suspicious, and some sources close to him are not exactly certain how Comey would respond to questions about how Trump's actions toward him now look in hindsight, knowing everything that has transpired since his firing.