James Comey. Zach Gibson/Getty Images

Former FBI Director James Comey is expected to testify in a public appearance before the Senate Intelligence Committee next week that President Donald Trump pressured him to end the bureau's investigation into Michael Flynn, the former national security adviser, according to multiple reports.

Comey has been cleared to testify by the Justice Department's special counsel, Robert Mueller, according to NBC News. After Trump fired Comey earlier this month, Deputy Attorney General Rod Rosenstein appointed Mueller to lead the criminal investigation into whether Trump's campaign colluded with Moscow during the 2016 election.

CNN on Wednesday cited a source close to Comey in reporting that he would "confirm bombshell accusations" that Trump "pressured him to end his investigation into a top Trump aide's ties to Russia."

The FBI is investigating Flynn's contact with Russian Ambassador Sergey Kislyak as part of its probe into Russia's interference in the 2016 election. The bureau interviewed Flynn about his conversations with Kislyak in January.

After asking Vice President Mike Pence and Attorney General Jeff Sessions to leave the room, Trump asked Comey during an Oval Office meeting in February to let the Flynn investigation go, according to a memo that Comey wrote that was read to The New York Times, which first disclosed the memo.

Weeks earlier, during a dinner on January 27, Trump reportedly twice asked Comey for his loyalty.

The Wall Street Journal also reported on Wednesday that a source close to Comey said he would confirm the Times report in his testimony.

Comey wrote the memo soon after meeting with Trump on February 14, one day after Flynn was asked to resign for misleading the vice president about his contacts with Kislyak. The memo "was part of a paper trail Mr. Comey created documenting what he perceived as the president's improper efforts to influence an ongoing investigation," according to The Times.

If it's found to be true that Trump asked Comey to drop the FBI's investigation into Flynn, "that would be very damaging," Keith Whittington, an expert on presidential impeachment and a politics professor at Princeton University, told Business Insider earlier this month.

Comey's memo fills in several details about Trump's ties to Russia and what the president's motives were in firing Comey, Whittington said.

Trump said days after firing Comey that he had been thinking about "this Russia thing" when he fired him. He called Comey a "showboat" and a "grandstander" in an interview with NBC's Lester Holt, and later tweeted: "James Comey better hope that there are no 'tapes' of our conversations before he starts leaking to the press!"