Tehran, Iran ? President Mahmoud Ahmadinejad called for the prosecution of Iran’s top opposition leaders Friday, backing hard-liners pushing for escalation of the postelection crackdown.

Ahmadinejad’s speech reflected the increasing bitterness of what has become Iran’s most tumultuous political crisis in decades.

While there were calls for unity in the weeks following the disputed June presidential election, the confrontation between the clerical leadership and the opposition has begun to look increasingly like an all-or-nothing fight.

Hard-liners in the leadership paint the entire reform movement as a tool of foreign enemies bent on overthrowing the cleric-led Islamic Republic. The opposition counters that the ruling system — beyond just Ahmadinejad’s elected government — is losing its religious and political legitimacy because of the harshness of the postelection crackdown.

More than 100 prominent opposition politicians and activists have been on trial on charges of seeking to topple the clerical leadership through a “velvet revolution.” But so far, the top rung of the opposition — Mir Hossein Mousavi, who claims to have won the June 12 election, and his allies Mahdi Karroubi and former President Mohammad Khatami — have not been touched.

Arresting them would dramatically escalate the confrontation. Earlier this week, Supreme Leader Ayatollah Ali Khamenei seemed to rule out doing so, saying he saw no evidence the top opposition leaders were “stooges” of foreign enemies.

The comments suggested Khamenei, who has strongly backed Ahmadinejad, was wary of provoking an even more widespread public backlash against his leadership.

Powerful forces, however, are pushing for their arrest, including senior hard-line clerics in the ruling establishment and commanders of the Revolutionary Guard.