Iran's opposition is planning a show of strength tomorrow on one of the country's most important political stages: the main Friday prayers in the nation's capital.

The top opposition supporter among Iran's clerical leaders is delivering this week's sermon. It's the first time that Ayatollah Hashemi Rafsanjani will do so since last month's disputed presidential election.

Pro-reform activists say they will pack the hall to prove their movement remains alive despite a government crackdown. Opposition leader Mir Hossein Mousavi says he'll be among them.

Hard-liners are also likely to attend, and that raises the prospect of a highly public confrontation. The prayers are broadcast live on national radio.

Government supporters have been pressuring Rafsanjani to make clear his loyalty to Supreme Leader Ayatollah Ali Khamenei in his sermon.