In the filing Manafort's lawyers said they would not seek an evidentiary hearing to contest Mueller's allegations of lying, arguing that such factual matters could be addressed in a pre-sentencing report.
Mueller, who is investigating Russia's interference in the 2016 election, said in a court filing in March previous year that the Federal Bureau of Investigation assesses that Kilimnik "has ties to a Russian intelligence service and had such ties in 2016".
Another revelation that was meant to be kept under wraps was a meeting between Manafort and Mr. Kilimnik in Madrid.
They contended the 69-year-old Manafort, facing years in prison, had breached the cooperation agreement that was reached when he pleaded guilty to cheating USA tax authorities, violating federal lobbying laws and obstructing justice in connection with his long-time lobbying efforts for deposed Ukrainian leader Viktor Yanukovych in the years before he worked on Trump's campaign. Prosecutors say Manafort violated their plea agreement by lying, but his defense insists it wasn't intentional and that his mistakes were due to illness, exhaustion and extensive questioning from investigators. They say he suffers from depression and anxiety, has been kept away from his family and, on days when he met with investigators, was awakened before dawn to have hours-long conversations with Mueller's team.
They say the circumstances of his confinement "weighed heavily on Mr. Manafort's state of mind and on his memory" as he was questioned.
Emails previously reported by news outlets show that in July 2016, Manafort told Mr Kilimnik he was willing to provide "private briefings" about the Trump campaign to Oleg Deripaska, a Russian billionaire with ties to Russian President Vladimir Putin.
A longtime Republican operative and lobbyist who had worked for prominent Republicans, including Bob Dole, Manafort joined the Trump campaign in March 2016.
Prosecutors also think Manafort and Kilimnik may have met in Madrid, during the campaign, to discuss a possible Ukraine peace plan, according to another passage of the new document. Russian Federation and Ukraine have been locked in a conflict since 2014 over Russia's annexation of Crimea. Six weeks after special counsel Robert Mueller's team announced that Manafort had lied to prosecutors after agreeing to cooperate with them, Manafort's attorneys filed an official response to Mueller's claims, arguing that Manafort "provided complete and truthful information to the best of his ability". This does not constitute outreach by Mr. Manafort to the President. His attorneys added that "it is not surprising at all that Mr. Manafort was unable to recall specific details prior to having his recollection refreshed".
The details about Manafort's alleged falsehoods come just as Russian lawyer Natalya Veselnitskaya, who famously attended a meeting with top Trump aides in 2016, was charged in a separate obstruction of justice case.
Mueller's team also indicted Kilimnik for witness tampering in Manafort's case.