Donald Trump Jr. tore into former White House chief strategist Steve Bannon Wednesday, deriding him as an "opportunist" who "squandered" the privilege of working for the Trump administration.

"Steve had the honor of working in the White House & serving the country," Trump Jr. wrote on Twitter.

"Unfortunately, he squandered that privilege & turned that opportunity into a nightmare of backstabbing, harassing, leaking, lying & undermining the President," he added. "Steve is not a strategist, he is an opportunist."

In excerpts published earlier Wednesday from media columnist Michael Wolff's upcoming book about the first year of the Trump presidency, Bannon is quoted describing the July 2016 Trump Tower meeting with Russian lawyer Natalia Veselnitskaya, organized and attended by President Trump's eldest son, as "treasonous" and "unpatriotic."

"They're going to crack Don Junior like an egg on national TV," Bannon said, according to excerpts from "Fire and Fury."