Mr. Moussavi, the defeated candidate who embodied the hopes of reformers, posted a notice on his Web site of a late afternoon rally in front of the Parliament, but he distanced himself from the action, saying it was not organized by the reform movement. It is not clear how far Mr. Moussavi, a former prime minister who is essentially an insider thrust into the role of opposition, would go to defy the system. He has not been seen since Thursday. So as the crackdown infuriates protesters, there is a greater gap with their ostensible leader, political analysts said.