Comey is scheduled to address the committee during the open hearing at Hart Senate Office Building in Washington, D.C., at 10 a.m.
The former FBI director will likely face questioning about his termination, the investigation into Russia's meddling in the U.S. election and encounters he had with Trump.
The committee on Wednesday released Comey's prepared remarks ahead of the hearing. In the prepared remarks, Comey plans to tell the Senate investigators that Trump asked him to end the investigation into former national security adviser Michael Flynn.
In his statement, Comey recalls several one-on-one conversations he had with Trump over four months -- three in person and six over the phone. He met privately with Trump in the Oval Office on February 14, one day after Flynn was fired.
"'I hope you can see your way clear to letting this go, to letting Flynn go,'" Comey quoted Trump as saying in his statement. "'He is a good guy. I hope you can let this go.'"
"I replied only that 'he is a good guy,'" the former bureau chief added. "I did not say I would let this go."
After the meeting, Comey wrote up details of the meeting in a memorandum -- standard procedure for a person in the FBI director's position, experts have noted.
"I immediately prepared an unclassified memo of the conversation about Flynn and discussed the matter with FBI senior leadership. I had understood the president to be requesting that we drop any investigation of Flynn in connection with false statements about his conversations with the Russian ambassador in December," Comey's statement continues. "I did not understand the president to be talking about the broader investigation into Russia or possible links to his campaign.
"It was very concerning, given the FBI's role as an independent investigative agency."
Comey agreed to testify before the Senate panel, which is conducting one of three U.S. investigations related to Russia, last week after receiving clearance from special investigator Robert Mueller.
Doug G. Ware contributed to this report.