Sen. Dianne Feinstein, D-Calif., gave a preview of the questions she will ask fired FBI Director James Comey during his upcoming public appearance before the Senate Intelligence Committee, which will seek answers on the number of times and topics that he spoke about with President Trump.

"How many times did he [Comey] meet with the president or talk with the president on the phone? What was he asked by the president? Was he asked to in any way alter the investigation? What was he asked about Mr. — Gen. Flynn? Questions like that," Feinstein told "Face the Nation" host John Dickerson.

Feinstein said the committee is no longer investigating whether President Trump's campaign associates colluded with Russia, but if he tried to cover it up and kill the federal probe by terminating Comey.

Feinstein, who is also the ranking Democrat on the Senate Judiciary Committee, said Comey's responses while under oath will be a better resource for the public to learn about the issue than the plethora of documents being requested from various congressional committees.

"I really think that rather than have all these memorandums and issues circulating around that we need to put the facts before the American people," said Feinstein. "Did the president fire Comey because of his investigation and he was worried about what the investigation might conclude? That, if so, that borders on a very serious charge."

However, Feinstein added she still wants to see Comey's memos about his meeting with Trump as well as the alleged White House tapes of their meetings.