Special counsel Robert Mueller plans to question former White House chief strategist Stephen Bannon about high-profile Trump administration firings, including the ouster of former FBI Director James Comey, CNN reported Wednesday.

Mueller wants to talk with Bannon about the firings of Comey, former national security adviser Michael Flynn and former acting Attorney General Sally Yates, CNN reported.

Mueller is reportedly expected to speak with Bannon, who left his White House role last summer, by the end of the month.

Bannon has called President Trump's decision to fire Comey the biggest mistake in "modern political history," arguing it led to Mueller appointment to investigate Russian election meddling, including potential ties between the Trump campaign and Moscow.

He sat down earlier this month with the House Intelligence Committee for its probe into Russian meddling in the 2016 presidential election. However, he frustrated lawmakers by refusing to answer questions about his time in the Trump administration, citing executive privilege.

CNN reported Wednesday that Bannon will not be able to use the same tactic with Mueller.

Mueller's probe has thus far led to two indictments and two guilty pleas.

Former Trump campaign chairman Paul Manafort and his former business associate, Richard Gates, were charged with money laundering and tax fraud, among other charges mostly related to the pair's work for a pro-Russia political party in Ukraine.

Flynn and former Trump campaign adviser George Papadopoulos pleaded guilty to lying to the FBI.

Mueller subpoenaed Bannon earlier this month as part of his investigation.

Bannon has fallen out of favor with Trump after he was quoted extensively in Michael Wolff's book "Fire and Fury: Inside the Trump White House."

In the book, Bannon criticizes Trump and his family, calling Donald Trump Jr.'s meeting with a Russian lawyer at Trump Tower in 2016 "treasonous" and "unpatriotic."

Trump issued a blistering rebuke of Bannon in response, saying he "lost his mind" when he left his White House job.