Most recently, Jerome Corsi, a conservative author and friend of the former Trump campaign aide Roger J. Stone Jr., said Mr. Mueller’s team is pressuring him to plead guilty to lying to them about his communications with Mr. Stone about WikiLeaks. Investigators are looking for links between the Trump campaign and WikiLeaks, which distributed emails and other documents that Russian agents stole from Democratic computers before the 2016 election. 
 
 Mr. Corsi said on Monday that he refused the plea deal because he did not deliberately mislead investigators, but merely forgot about an email chain from two and a half years ago. 
 
 In his most recent criticism of the special counsel, Mr. Trump has suggested that prosecutors are frustrated because they cannot produce any evidence against his campaign. “The inner workings of the Mueller investigation are a total mess,” he wrote on Twitter recently. 
 
 “They have found no collusion and have gone absolutely nuts. They are screaming and shouting at people, horribly threatening them to come up with the answers they want,” he declared. “They are a disgrace to our Nation and don’t care how many lives” they ruin. 
 
 Mr. Trump’s lawyers responded last week to questions Mr. Mueller had for the president about ties between his campaign and Russia. Among the questions were inquiries about what Mr. Trump knew about Russian offers to Mr. Manafort during the campaign to assist Mr. Trump’s presidential run. The president’s lawyers have declined to discuss what he told Mr. Mueller, and it is not clear whether any of his answers conflicted with what Mr. Manafort told investigators. 
 
 Mr. Manafort’s allies have hoped that his sessions with the special counsel would end soon so he could be sentenced and transferred to a federal prison, where conditions are comparatively better than in a local jail. At a recent court hearing in Alexandria, Mr. Manafort came into the courtroom in a wheelchair, his foot wrapped in a white bandage, possibly from an attack of gout. 
 
 But few of Mr. Manafort’s friends predicted that his sentencing would be hastened by prosecutors declaring him to be a liar. The development stunned some people close to the White House, as well as legal experts. 
 
 “Everybody who lies to Mueller gets called on it — so he had to know that Mueller would catch him. So the question is: What was he hiding that is worse than going to jail for the rest of your life?” said Joyce Vance, a professor of law at the University of Alabama law school and former federal prosecutor. “There are often rocky dealings with a cooperator, and Mueller didn’t cut bait at the first sign of trouble. It was likely more than one lie and this would not have been a minor detail — it had to be something material and significant and intentional.” 

 FILE - In this May 23, 2018, file photo, Paul Manafort, President Donald Trump's former campaign chairman, leaves the Federal District Court after a hearing, in Washington. Special counsel Robert Mueller... (Associated Press) 
 
 FILE - In this May 23, 2018, file photo, Paul Manafort, President Donald Trump's former campaign chairman, leaves the Federal District Court after a hearing, in Washington. Special counsel Robert Mueller is accusing Manafort of lying to federal investigators in the Russia probe in breach of his plea... (Associated Press) 
 
 FILE - In this May 23, 2018, file photo, Paul Manafort, President Donald Trump's former campaign chairman, leaves the Federal District Court after a hearing, in Washington. Special counsel Robert Mueller is accusing Manafort of lying to federal investigators in the Russia probe in breach of his plea... (Associated Press) FILE - In this May 23, 2018, file photo, Paul Manafort, President Donald Trump's former campaign chairman, leaves the Federal District Court after a hearing, in Washington. Special counsel Robert Mueller... (Associated Press) 
 
 WASHINGTON (AP) — The special counsel in the Russia investigation is accusing former Trump campaign chairman Paul Manafort of violating his plea agreement by repeatedly lying to federal investigators, an extraordinary allegation that could expose him to a lengthier prison sentence — and potentially more criminal charges. 
 
 The torpedoing of Manafort's plea deal, disclosed in a court filing Monday, also results in special counsel Robert Mueller's team losing a cooperating witness from the top of Donald Trump's presidential campaign who was present for several key episodes under investigation. That includes a Trump Tower meeting involving Donald Trump Jr. and a Russian lawyer he was told had derogatory information on Democrat Hillary Clinton. 
 
 The move signals a return to the acrimonious relationship Manafort has had with the special counsel's office since his indictment last year. Before his plea agreement, Manafort aggressively challenged the special counsel's legitimacy in court, went through a bitter trial and landed himself in jail after prosecutors discovered he had attempted to tamper with witnesses in his case. 
 
 In the latest filing, Mueller's team said Manafort "committed federal crimes" by lying about "a variety of subject matters" even after he agreed to truthfully cooperate with the investigation. Prosecutors said they will detail the "nature of the defendant's crimes and lies" in writing at a later date to the judge. 
 
 Through his attorneys, Manafort denied lying, saying he "believes he provided truthful information" during a series of sessions with Mueller's investigators. He also disagreed that he breached his plea agreement. Still, both sides now agree they can't resolve the conflict, and U.S. District Judge Amy Berman Jackson should set a date to sentence him. 
 
 Manafort, who remains jailed, had been meeting with the special counsel's office since he pleaded guilty in September to conspiracy against the United States and conspiracy to obstruct justice. He cut that deal to head off a second trial after being convicted last summer of eight felony counts related to millions of dollars he hid from the IRS in offshore accounts. 
 
 Both cases stemmed from his Ukrainian political work and undisclosed lobbying work he admitted to carrying out in the U.S. in violation of federal law. 
 
 As part of his plea agreement, Manafort pledged to "cooperate fully, truthfully, completely, and forthrightly" with the government "in any and all matters" prosecutors deemed necessary. That included his work on the Trump campaign as well as his Ukrainian political work, which remains under investigation by the U.S. attorney for the Southern District of New York. 
 
 Prosecutors there are looking into the conduct of longtime Democratic lobbyist Tony Podesta, former Obama White House counsel Greg Craig and former Republican congressman and lobbyist Vin Weber to determine whether they violated federal law by failing to register as foreign agents with the Justice Department. None of the men has been charged with any crimes. 
 
 As part of his plea deal, Manafort also forfeited many of his rights as well as his ability to withdraw the plea if he broke any of the terms. In return, prosecutors agreed to not bring additional charges against him and to ask a judge for a reduction of his sentence if he provided "substantial assistance." 
 
 But with prosecutors saying he breached the agreement, Manafort now faces serious repercussions such as the possibility of prosecution on additional charges including the 10 felony counts prosecutors dropped when he made the deal. 
 
 Manafort already faces up to five years in prison on the two charges in his plea agreement. In his separate Virginia case, Manafort's potential sentencing under federal guidelines has not yet been calculated, but prosecutors have previously said he could face as much as 10 years in prison on those charges. 
 
 He is scheduled to be sentenced in that case in February. His co-defendant, Rick Gates, who spent a longer time on the campaign and worked on the Trump inaugural committee, has not had a sentencing date set yet. He continues to cooperate with Mueller. 
 
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 Follow Chad Day on Twitter: https://twitter.com/ChadSDay 
 
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 Read the court filing: http://apne.ws/YN2AwkK
– The Robert Mueller investigation just lost an important witness—and Paul Manafort may have lost additional years of freedom. In a court filing Monday, the special counsel's team said President Trump's former campaign chairman had violated a plea agreement by repeatedly lying to federal investigators. The team said Manafort had "committed federal crimes" by lying about "a variety of subject matters" after he had pledged to cooperate "fully and truthfully" with investigators, the AP reports. The filing suggests Mueller's team doesn't consider Manafort a credible witness—and in any case, after publicly calling him a liar, "they could hardly call him to testify," the New York Times notes. The court filing stated that "the nature of the defendant’s crimes and lies" will be outlined in a sentencing submission from the government, the Washington Post reports. Manafort's lawyers say he "believes he provided truthful information" to Mueller's investigators. Manafort, currently being held in solitary confinement in a Virginia detention center, cannot withdraw his guilty plea under the terms of the deal, though he can now be prosecuted for additional crimes—including the 10 felony charges that were dropped when he made the agreement. Prosecutors had also agreed to ask for a reduction of his sentence if he provided "substantial assistance." Manafort is expected to be sentenced to at least 10 years for crimes including conspiracy to obstruct justice. (Manafort looked very different at a hearing last month.)