The release of an American woman detained on suspicion of spying will not go ahead on Saturday as had been previously announced, an Iranian official says.
Sarah Shourd, 31, and two other hikers were arrested in July 2009 after they crossed the Iran-Iraq border.
Tehran's prosecutor general said Ms Shourd would not be freed because legal procedures were not complete.
Iran initially said Ms Shourd, Shane Bauer and Josh Fattal would be put on trial for espionage - an offence that can be punishable by death.
The BBC reports Ms Shourd is believed to be suffering from potentially serious health problems, and that the authorities had said she would be freed as a goodwill gesture for the Muslim holiday of Eid al-Fitr.
A BBC correspondent says it sounds as if her case has fallen victim to the increasingly bitter power struggle between elites in Iran.
The United States says the three hikers have committed no crime, and has appealed for their immediate release.
