Comey will stop short of saying Trump obstructed justice in Flynn probe, source says Sources familiar with Comey's thinking preview his highly anticipated testimony.

 -- There will be much in former FBI Director James Comey’s upcoming congressional testimony that will make the White House uncomfortable, but he will stop short of saying the president interfered with the agency's probe into former national security adviser Michael Flynn, a source familiar with Comey's thinking told ABC News.

Although Comey has told associates he will not accuse the president of obstructing justice, he will dispute the president’s contention that Comey told him three times he is not under investigation.

UPDATE: While Comey did stop short of characterizing Trump’s words as obstruction of justice during his testimony Thursday, he in fact testified that he did tell President Trump on three separate occasions that he was not “personally” the subject of a counter-intelligence investigation. Comey also acknowledged that there was an internal debate within his leadership team as to whether that would be an accurate statement given the fact that the investigation was looking into possible Russian collusion with Trump’s presidential campaign. Ultimately, Comey said he believed it would be correct to tell the President he was not personally the subject of an investigation.

The president allegedly said he hoped Comey would drop the Flynn investigation, a request that concerned Comey enough that he documented the conversation in a memo shortly after speaking with the president. In the memo, according to sources close to Comey who reviewed it, Trump said: "I hope you can see your way clear to letting this go, to letting Flynn go," during a February meeting.

The request made Comey uncomfortable, but the source tells ABC News that Comey has told associates he will not accuse the president of obstructing justice.

“He is not going to Congress to make accusations about the president’s intent, instead he’s there to share his concerns,” the source said, and tell the committee “what made him uneasy” and why he felt a need to write the memo documenting the conversation.

Some legal experts told ABC News that Trump's requests as detailed in the memo, which ABC News has not seen, could meet the legal definition of obstruction.

Comey told associates he plans to testify that despite the unusual request from the president he believed strongly that if he did his job properly he could conduct the investigation in an honest way.

However, Comey has told associates he will not corroborate Trump's claim that on three separate occasions Comey told the president he was not under investigation as part of the probe into Russian meddling in the U.S. election, a source familiar the former director’s thinking told ABC News.

When the president fired Comey early last month he wrote him a letter saying, “While I greatly appreciate you informing me, on three separate occasions, that I am not under investigation, I nevertheless concur with the judgment of the Department of Justice that you are not able to effectively lead the Bureau.”

Comey's associates have insisted in recent weeks that Comey would never have offered such assurances, even to the president, as a matter of principle. The FBI has confirmed publicly that it is conducting an investigation into Russian meddling and possible collusion with the Trump campaign, but it has not named names.

The New York Times first reported last month that Trump asked Comey to shut down the Flynn investigation. “I hope you can see your way clear to letting this go, to letting Flynn go,” Trump allegedly told Comey. “He is a good guy. I hope you can let this go.”

Trump was asked directly at a press conference last month if he had "in any way, shape or form" asked Comey to "back down the investigation into Michael Flynn," and he strongly denied it.

"No. No. Next question," Trump responded to the reporter.

Comey is scheduled to testify publicly for the first time since he was fired at a hearing in front of the Senate Intelligence Committee at 10 a.m. on Thursday.

*This story has been updated to reflect that Comey testified he did in fact tell the president on three occasions he was not the subject of an investigation.