Prosecutors claim he assisted Manning in cracking a password to help her leak classified records to the whistleblowing website.
Assange was convicted of breaching his bail conditions after entering the Ecuadorian embassy while wanted over allegations of sexual offences in Sweden, which he denies.
After Assange was jailed, lawyer Jennifer Robinson vowed that the “focus of our energies will now be on fighting” the US extradition request.
The Australian is not expected to be in court in person, and will instead appear via a videolink from prison.