President Trump was "furious" when he was first made aware of the incendiary comments Steve Bannon made about his son, Donald Trump Jr., in a new book due out next week, the White House said Wednesday, hours after Trump claimed his former chief strategist "lost his mind" when he left the West Wing last August.

"Furious' [or] 'disgusted' would probably fit when you make such false claims about the president and his administration," press secretary Sarah Sanders told reporters when asked how Trump felt about excerpts from the book by veteran journalist Michael Wolff.

Sanders said "a number of factors" led to the fallout between Trump and Bannon. The current Breitbart chairman exited the White House last summer and sowed discord in Republican politics late last year when he hit the campaign trail to actively support defeated Senate GOP candidate Roy Moore in Alabama.

But describing the infamous Trump Tower meeting between Trump Jr. and a Russian lawyer as "treasonous" may have been the last straw for Bannon, whose most recent conversation with the president took place in early December.

"I would certainly think that going after the president's son in an absolutely outrageous and unprecedented way is probably not the best way to curry favor with anybody," Sanders said.