Roger Stone, former campaign adviser to U.S. President Donald Trump, arrives for his criminal trial on charges of lying to Congress, obstructing justice and witness tampering at U.S. District Court in Washington, November 6, 2019.

One former top advisor to President Donald Trump is going to testify against another in a federal criminal trial in Washington.

Former White House chief strategist Steve Bannon will testify against Trump's longtime political advisor and confidant Roger Stone, prosecutors said Wednesday.

Bannon is not a voluntary witness, according to a person with direct knowledge of the matter. Rather, he was commanded to testify by prosecutors after he and his legal team fought off numerous subpoenas, said the person, who declined to be named.

Stone, a self-described "dirty trickster," is accused of obstructing justice, witness tampering and lying to the House of Representatives' Intelligence Committee. The case stems from special counsel Robert Mueller's investigation. Stone has denied all wrongdoing.

"This case is not about who hacked the DNC's servers. This case is not about whether Roger Stone had any communication with any Russians. This case is not about politics," prosecutors said. "This case is about Roger Stone's false testimony to the House Intelligence Committee."

Former top Trump campaign official Rick Gates was also set to testify against Stone.

Bannon, Gates and Stone were all key figures in Mueller's investigation into whether Russia interfered in the 2016 presidential election.

Bannon was a key witness for Mueller and his team. Records recently made public by the FBI show that he discussed his role as the campaigns chief executive and, later, as a member of Trump's administration.

Bannon's attorney and spokeswoman did not return a request for comment.

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During the Mueller investigation, The New York Times obtained a batch of emails showing Stone reached out to Bannon about Julian Assange, the founder of WikiLeaks. Their conversations came prior to the now infamous email dump by WikiLeaks that made public communications involving Hillary Clinton's campaign chairman, John Podesta. Clinton would lose the general election a month later to Donald Trump.

Mueller concluded that Russia did, in fact, interfere in the 2016 presidential election and left it up to Congress to decide whether Trump and his administration obstructed justice throughout his investigation.

Gates, who had previously testified against former Trump campaign boss Paul Manafort, pleaded guilty in the Mueller probe and is awaiting sentencing.