President Donald Trump's former chief strategist Steve Bannon has been subpoenaed by Special Counsel Robert Mueller to testify before a grand jury in a probe into alleged ties between Russia and Trump's 2016 presidential campaign, the New York Times reported on Tuesday.
It was the first time Mueller is known to have used a subpoena against a member of Trump's inner circle, the Times said. It cited a person with direct knowledge of the matter.
A spokesman for Mueller's office declined comment. Bill Burck, a lawyer for Bannon, could not immediately be reached for comment.
Bannon, a champion of Trump's "America First" agenda, was among the Republican's closest aides during the 2016 election campaign, the presidential transition and during his first months in office.
But the pair had a bitter public falling out over comments Bannon made to author Michael Wolff for his recent book "Fire and Fury: Inside the Trump White House."
In the book, Bannon is quoted as describing a June 2016 meeting between Trump associates, including the president's son Donald Trump Jr, his son-in-law, Jared Kushner, and a Russian lawyer, as "treasonous" and "unpatriotic."
The meeting came after Donald Trump Jr was told in an email that the Russian government had compromising information about Democratic presidential candidate Hillary Clinton, to which he replied: "I love it."
Bannon was fired by the White House in August and returned to the right-wing news website Breitbart News. He continued to speak with Trump and tried to promote the president's agenda.
But Trump accused Bannon of having "lost his mind" when news of his comments to Wolff surfaced earlier this month. Six days later, Bannon stepped down from his post as executive chairman at Breitbart News.
Mueller's subpoena, which was issued last week, could be a pressure tactic to induce Bannon to cooperate fully with his investigation, the Times reported.
Separately on Tuesday, Bannon was meeting with the House of Representatives Intelligence Committee. He is the latest high-profile figure to testify before the panel as part of its investigation into Russia interference in the US election.
Russia has denied meddling in the election and Trump has denied there was any collusion between his campaign and Moscow.
Later in the week, the panel will hear from former Trump campaign manager Corey Lewandowski.
White House Communications Director Hope Hicks, who served as Trump's spokeswoman during his presidential campaign after a tenure with his Trump Organization real estate business, is also expected to be questioned by the committee this week, according to a congressional source.
Democrats on the committee have accused Republicans of rushing to wrap up the probe to help give the president political cover, despite their requests to interview more witness. Republicans have denied the charge.
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