The new plea in the Washington federal district court was required after prosecutors added new charges against him last week. First made public on October 30, the indictment was revised again after Manafort's former partner, Richard Gates, entered a guilty plea, promising to cooperate with Mueller's investigation.
Manafort, 68, is accused of laundering some $75 million in relation to his and Gates' work for Russia-backed former Ukraine president Viktor Yanukovych between about 2006 and 2014.
A trial was scheduled to begin on September 17.
A long-time Washington and international political consultant, Manafort became President Donald Trump's election campaign chairman in June 2016 and made Gates his deputy.
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Manafort stepped down two months later over the Ukraine investigation, but Gates remained on the campaign and worked for Trump through the transition period after Trump's November 2016 election viictory.
On Friday, Gates pleaded guilty to much-reduced charges of fraud and lying and promising to cooperate fully with Mueller's sprawling probe into whether the Trump campaign colluded with Russians to illegally interfere with the election.
Manafort also faces separate charges for bank fraud and tax evasion that were filed Friday by Mueller's team in a Virginia court. Parallel charges against Gates were dropped.
Manafort was defiant, refusing to cut a deal.
"Notwithstanding that Rick Gates pled today, I continue to maintain my innocence," he said Friday in a statement.
"I had hoped and expected my business colleague would have had the strength to continue the battle to prove our innocence ... This does not alter my commitment to defend myself against the untrue piled up charges contained in the indictments against me.
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