The immunity request specifies that the "named individuals will not testify or provide other information" without it, because of the protections against "self-incrimination".
As a result, prosecutors are asking a judge to compel their testimony, under a condition of immunity, at Manafort's upcoming bank and tax fraud trial. However, they would still be vulnerable to prosecution for perjury if they lied under oath.
The decision to grant immunity would in theory prevent witnesses from refusing to answer specific questions when testifying against Mr Manafort.
Mueller says the witnesses haven't been publicly identified in the case, and haven't been charged.
Manafort's prosecution arose out of U.S. Special Counsel Robert Mueller's investigation into possible collusion between Russian Federation and U.S. President Donald Trump's 2016 presidential campaign.
Under fire, Trump says he misspoke on Russian Federation election meddling
Trump chose before, ultimately putting the issue into the spotlight just 72 hours before the high-stakes meeting, the people said. If Putin was looking for a more pro-Moscow policies from the United States, his election interference backfired in a big way.
Manafort's lawyers said extensive pretrial news media coverage in the Washington region had interfered with Manafort's right to a fair trial.
The cases are U.S. v. Manafort, 17-cr-201, U.S. District Court, District of Columbia (Washington), and 18-cr-83, U.S. District Court, Eastern District of Virginia (Alexandria).
A handout photo made available by the Alexandria Virginia Sheriff's Office shows former Trump campaign chairman Paul Manafort mug shot, Alexandria, Virginia, USA (issued 12 July 2018).
The trial is one of two at which Manafort must defend himself against a number of charges ranging from bank fraud to failing to register as a foreign agent for lobbying work for pro-Russia politicians in Ukraine. The trial publicity, Ellis argued, would be the same if the trial was happening in "Roanoke or Kansas City".