Former White House chief strategist Steve Bannon has reportedly called a meeting between Donald Trump's son and a Russian lawyer during the 2016 election campaign "treasonous" - drawing an angry response from the US president.

"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, who sacked Bannon in August, said in a statement.

"Steve doesn't represent my base," he said, adding that Bannon is "only in it for himself".

Trump's comments on Wednesday came in response to the release of excerpts from the upcoming book, Fire and Fury: Inside the Trump White House, written by investigative journalist Michael Wolff.

Russian probe

Al Jazeera's Diane Eastabrook, reporting from Washington, DC, said the book contained "explosive allegations".

She said Bannon's "treason" comment was referring to a meeting Donald Trump Jr took with Natalia Veselnitskaya in June 2016 after an intermediary promised material that would potentially incriminate Trump's Democratic rival, Hillary Clinton.

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"In this book, allegedly Bannon says that [this] should have been reported, that Donald Trump Jr should have immediately gone to the FBI with that information and because that he actually accepted that meeting with this woman to potentially get this dirt was treasonous," said Eastabrook.

The excerpts were first reported by British newspaper The Guardian, which obtained an early copy of the book, which is expected to be published next week.

Containing some 200 interviews from people inside the White House, Wolff's book reportedly paints Trump as a juvenile in many ways who does not understand the weight of his role and spends his evenings eating cheeseburgers in bed, watching TV and talking on the phone to his old friends.

The release of the excerpts comes as Robert Mueller, a former FBI director, is leading an investigation into whether the Trump campaign colluded with Russia to get him elected. Trump has repeatedly denied the allegation.

"That is why you are seeing this forceful pushback by the US president," said Eastabrook.

Working closely

In his statement, Trump also said that Bannon was "rarely in a one-on-one meeting" with him.

Eastabrook noted, however, that the president's claim was "really questionable", underlining the two men's close ties.

"Steve Bannon came in in the late summer of 2016 to run Trump's campaign," she said. "He then became a chief strategist for the transition and then came into the White House as his chief political strategist."

The former head of far-right outlet Breitbart News, Bannon has been labelled by critics a white supremacist.

After joining Trump's campaign, he helped the president draft a controversial travel and immigration ban from several Muslim-majority countries.

According to Wolff's book, Bannon was encouraging Trump to name Jerusalem as Israel's capital shortly after taking office.

The US president eventually did so on December 6, provoking Palestinian anger and widespread condemnation by the international community.