Former FBI deputy director wrote memo detailing discussion with deputy attorney general: Source

Details of the memo were first reported by the New York Times.

Details of the memo were first reported by The New York Times.

ABC News has not seen the memo, but according to the source, it describes what Rosenstein told McCabe: that President Donald Trump wanted Rosenstein to include a reference to Russia in his memo criticizing Comey.In the end, Rosentein's May 9, 2017, memo, which was used by Trump as a basis for firing Comey, did not mention Russia. Instead, Rosenstein's memo focused on Comey's handling of the Clinton email investigation.

The suggestion that the president requested the memo mention the Russia investigation could provide ammunition to any allegation that Trump fired Comey in part to impede the investigation. However, the Times report also suggests alternative explanations, such as Trump’s desire to make clear he was not the target of the Russia probe.

McCabe wrote multiple memos, including some related to the president, and all of them are now in the hands of special counsel Robert Mueller, according to the source.

McCabe was fired just days before his retirement after a finding by the Justice Department's Inspector General that he "lacked candor" when talking to internal investigators about his role in a disclosure to the media.

Mueller's team is investigating Comey's firing and whether anyone may have sought to obstruct justice, sources have told ABC News.

The McCabe memo describing his meeting with Rosenstein underscores the unusual position the deputy attorney general is in -- he is overseeing the Mueller probe while also being a potential witness in the investigation.

Rosenstein was interviewed by Mueller's team last summer.