Hard-line lawmakers called for Mahdi Karroubi and two other prominent pro-reform figures to be brought to trial and put to death in response to demonstrations earlier in the week.
The demonstrations were meant to show solidarity with those behind Egypt's uprising, but also highlighted Iran's own simmering unrest. Two protesters were killed in clashes with police.
Karroubi said Wednesday on his website, sahamnews.net, that he was willing to "pay any price" to bring social and political changes to Iran. He is one of several leaders of a protest movement that grew out of the disputed presidential election in 2009.