Some reporters for Iranian media will be admitted to the 9:00 am (0430 GMT) hearing before the Tehran revolutionary court but foreign media will be barred, IRNA said.
Iran has put about 140 protesters on trial for contesting the re-election of President Mahmoud Ahmadinejad in the June 12 poll.
Those on trial include leading reformist politicians, activists and employees of the British and French embassies.
The opposition has denounced what it has called a "show trial".
The post-election unrest left 36 people dead, according to Iranian officials, but opposition groups say 72 people died, some of them in police custody.
