(Reuters) - Sam Nunberg, a former political aide to Donald Trump, will be interviewed on Thursday as part of a U.S. special counsel's investigation of Russian meddling in the 2016 election, two people with knowledge of the matter said.

Nunberg started working for then-businessman Trump in 2011, making him one of his earliest political advisers, but he was fired from the Republican's campaign in August 2015 before the heat of the 2016 presidential race.

Nunberg's interview in Washington with U.S. Special Counsel Robert Mueller is about a week after investigators questioned President Trump's former chief strategist Steve Bannon. Nunberg visited Bannon in the West Wing and considers him a close friend, according to an interview with Newsmax last year.

Nunberg, 36, is also an associate of Trump ally and longtime political consultant Roger Stone.

Patrick Brackley, the attorney who will accompany Nunberg to visit Mueller's team, could not immediately be reached for comment.

Mueller's investigation arose in part from the findings of U.S. intelligence agencies that Russia had meddled in the election and that its goals eventually included aiding Trump who won a surprise victory over Democrat Hillary Clinton. Russia denies the allegations and Trump says there was no collusion between Moscow and his campaign.

Mueller has charged several Trump associates and more than a dozen Russians.

Nunberg has had an on-off relationship with Trump over the years. He was dismissed months into the presidential campaign after Business Insider reported that he had written racially- charged Facebook posts in 2007. Nunberg told Business Insider he did not remember writing them and apologized.

Trump later sued Nunberg seeking damages of $10 million, saying the former aide had broken a confidentiality agreement. The lawsuit was settled in August 2016 and the one-page filing in a New York court did not provide details of the terms.

Nunberg said in a court filing in the case that Trump accused him of being the source for a media report about an argument between two other Trump campaign aides, Corey Lewandowski and Hope Hicks.

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Nunberg denied being the source for the media report.

In an affidavit, Nunberg said the argument was part of an affair between Lewandowski, then Trump's campaign manager, and Hicks, then Trump’s spokeswoman and now White House communications director.

At the time Alan Garten, a lawyer for the Trump Organization, called Nunberg’s allegations "categorically untrue."

(reporting by Nathan Layne in Washington; additional reporting by Steve Holland; editing by Grant McCool)