Former Trump campaign chairman Paul Manafort pleaded guilty in federal court Friday as part of a plea agreement that involves cooperation with Special Counsel Robert Mueller and allows him to avoid a second trial.

“I plead guilty," Manafort, 69, told U.S. District Judge Amy Berman in Washington.

Prosecutor Andrew Weissmann told the judge that Manafort's deal includes a cooperation agreement with prosecutors, who are investigating whether any Trump associates played a role in Russia's meddling in the 2016 election. That could include interviews with prosecutors and testifying in court.

A defense attorney for Manafort told Fox News the deal includes "full cooperation."

But the president's team downplayed the significance of Manafort's plea.

“Once again an investigation has concluded with a plea having nothing to do with President Trump or the Trump campaign," Trump lawyer Rudy Giuliani said in a statement to Fox News. "The reason: the president did nothing wrong."

White House press secretary Sarah Sanders said Friday that Manafort's decision is "totally unrelated" to the president.

Manafort, in a trial set to begin Sept. 24, had been facing seven counts of foreign lobbying violations and witness tampering in federal court in Washington.

In August, in a separate trial in Virginia, a federal jury found Manafort guilty on eight counts of federal tax and banking crimes.

Manafort faces up to 10 years on these charges in Washington. He still faces sentencing for his guilty verdict in Virginia.

As part of this agreement, Manafort has forfeited multiple bank accounts and several properties in New York. However, he will keep his properties in Florida and Virginia, where his family live.

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Manafort attorney Kevin Downing told reporters after the court hearing it was a “tough day” for his client, “who has accepted responsibility.” He said Manafort “wanted to make sure that his family was able to remain safe and live a good life.”

The case was brought by Mueller's team, which is probing potential crimes related to the 2016 election. But Manafort has not been charged with anything related to the campaign.

In August, Manafort’s bank and tax fraud conviction made him the first campaign associate of Trump found guilty by a jury as part of Mueller’s probe.

“I feel very badly for Paul Manafort,” Trump told reporters after the August verdict, adding that it had "nothing to do with Russian collusion." The president has called Mueller's probe a "witch hunt."

Trump also said he had “such respect” for Manafort and called him a “brave man.” In comments interpreted to mean he was open to pardoning Manafort, Trump commended Manafort, saying he “refused to break” and “make up stories in order to get a deal.”

In the Virginia trial, prosecutors said Manafort hid income earned from political work overseas from the IRS while fraudulently obtaining millions in bank loans. Manafort had pleaded not guilty to all counts.

The prosecution’s star witness, Rick Gates – Manafort’s former business partner who struck a plea deal to cooperate with the government -- testified during the trial that he and Manafort committed bank and tax fraud together.

Downing, Manafort's attorney, suggested after the guilty verdict in August that Manafort was open to striking a deal before the second trial.

“He is evaluating all of his options at this point,” Downing said of Manafort.

Fox News' Catherine Herridge, John Roberts and NuNu Japaridze contributed to this report.