"Mr. Manafort, moreover, is now housed in solitary confinement because the facility cannot otherwise guarantee his safety," the document said. "He is locked in his cell for at least 23 hours per day (excluding visits from his attorneys), at a facility approximately two hours from his legal team."
Manafort’s lawyers have argued that his confinement two hours away from Washington is complicating trial preparations.
Mueller had previously charged Manafort with money-laundering conspiracy and acting as an unregistered foreign agent for work he did for the Ukrainian government. The Special Prosecutor is also probing allegations that Russia interfered in the 2016 US presidential election, as well as accusations that Trump's campaign team colluded with Moscow.
Russian officials have repeatedly denied allegations of interference, calling the accusations absurd and intended to deflect public attention from actual instances of election fraud and corruption as well as other issues.