Former White House chief strategist Steve Bannon called a June 2016 meeting with a group of Russians attended by Donald Trump Jr. and his father's top campaign officials "treasonous" and "unpatriotic," according to excerpts of a new book seen by Reuters on Wednesday.

The explosive comments from a former close aide and far-right architect of Donald Trump's November 2016 election victory roiled the White House and the Republican president, who famously values loyalty in associates and employees. Trump fired Bannon from his White House post in August and split with him on Wednesday in a highly personal public repudiation.

"Steve Bannon has nothing to do with me or my presidency. When he was fired, he not only lost his job, he lost his mind," Trump said in a statement hours after Bannon's comments emerged.