Mueller last month accused Trump's former campaign chairman Paul Manafort of breaching a plea bargain deal by lying to prosecutors.
US Special Counsel Robert Mueller will provide new details on Friday on how two of President Donald Trump's closest former aides have helped or hindered his investigation into possible collusion between Russia and Trump's 2016 election campaign.
Mueller last month accused Trump's former campaign chairman Paul Manafort of breaching a plea bargain deal by lying to prosecutors, and he will submit information on those alleged lies in a filing to a federal court in Washington.
That could include shedding new light on Manafort's business dealings or his consulting for pro-Kremlin interests in Ukraine.
Manafort, who maintains he has been truthful with Mueller, managed Trump's campaign for three months in 2016.
Also on Friday, Mueller's office and the Southern District of New York are to file sentencing memos on Michael Cohen, Trump's former private lawyer.
Cohen pleaded guilty to financial crimes in a New York court in August, and last week to lying to Congress in a Mueller case. Sentencing for both of those cases will be handled by one judge.
Attention will focus on whether Mueller discloses new information to supplement Cohen's admission last week that he sought help from the Kremlin for a Trump skyscraper in Moscow late into the 2016 campaign.
Mueller's probe has infuriated Trump. He denies any collusion between his team and Russia, and accuses Mueller's prosecutors of pressuring his former aides to lie about him, his election campaign and his business dealings.
The president has called Cohen a liar and "weak person."
Renato Mariotti, a former federal prosecutor, said he was eager to see if Mueller's prosecutors directly or tacitly support Cohen's assertions that Trump directed him to make hush payments to women in violation of campaign finance law and that he let the White House know what he planned to tell Congress about the Moscow skyscraper project. Cohen now says he lied in that testimony.
"If the government does not contest that, it indicates that it is consistent with the evidence that they do have," Mariotti said, referring to Cohen's assertions. "It could be a big day."
Sending a message?
The filings on Cohen and Manafort follow a sentencing memo earlier this week on Trump's former national security adviser Michael Flynn.
In that memo, Mueller praised Flynn for providing "substantial" cooperation and argued that Flynn should receive no prison time, a move widely seen by legal experts as a message to other would-be cooperators that assistance would be rewarded.
Cohen is hoping he will get similar credit, emphasizing in a court filing last week that his decision to cooperate came in the face of fierce criticism by Trump of Mueller's probe.
Cohen's lawyers also argued that celebrities engaged in similar tax evasion cases - one of the core charges against him - faced only civil penalties. They said his financial crimes were unsophisticated, noting no overseas accounts were used.
Manafort, in addition to allegedly lying to Mueller, was convicted in a separate case in Virginia for a sophisticated bank and tax fraud scheme that included tens of millions of dollars in payments for his work in Ukraine.
Mariotti said he expected Mueller's office to be unsparing in its submission on Friday.
"They want the judge to throw the book at Manafort, sending a message to him and everyone else," he said.