Seeing as how they already have his testimony from his plea, my only conclusion is that the prosecutors are trying to suborn perjury against Assange:
Chelsea Manning was again behind bars on Thursday night after she was jailed for a second time for contempt of court, having refused to cooperate with a grand jury.
A defiant Manning told Judge Anthony Trenga in a federal district court in Alexandria, Virginia, that she would “rather starve to death” than do what the state insisted and give testimony before the grand jury. Having already served 62 days in jail, 28 of which were spent in solitary confinement, she now faces up to 18 months more in custody.
To quote Anatole France, “The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges.”