WASHINGTON - Steve Bannon, former White House chief strategist, apologized on Sunday for comments he had made and was quoted in a new controversial book calling US President Donald Trump's eldest son's 2016 meeting with Russians "treasonous and "unpatriotic".

"Donald Trump, Jr. is both a patriot and a good man. He has been relentless in his advocacy for his father and the agenda that has helped turn our country around," Bannon said in a statement to news website Axios, breaking five days of silence since his comments were revealed.

"My comments were aimed at Paul Manafort, a seasoned campaign professional with experience and knowledge of how the Russians operate," Bannon said. "He should have known they are duplicitous, cunning and not our friends."

"My support is also unwavering for the president and his agenda," Trump's ex top strategist said, adding he regrets his delay in responding to the inaccurate reporting regarding Trump's eldest son.

Britain's The Guardian newspaper on Wednesday first revealed that Bannon, quoted from excerpts of the book "Fire and Fury: Inside the Trump White House," described the 2016 meeting at Trump Tower between a Russian lawyer and Trump' s son and son-in-law as " treasonous" and " unpatriotic."

Later on Wednesday, Trump said in a White House official statement that Bannon had "lost his mind" and had "no influence" within his government.

White House Press Secretary Sarah Huckabee Sanders also fiercely slapped Michael Wolff's book -- Fire and Fury, saying that it is "filled with false and misleading accounts," adding that Trump felt "furious" and" disgusted" about Bannon's comments in the book.

Since then, Bannon has been greatly isolated from his political allies and conservative donors, including billionaire Rebekah Mercer and her father Robert Mercer.

Bannon was chief executive of the Trump campaign in its final three months during the 2016 US elections. He became the White House chief strategist after Trump took office in Jan. 2017 and left the White House in August before returning to his perch as chairman of right-wing Breitbart News.