The three American hikers accused of espionage by Iran stepped off an unmarked dirt road - inadvertently crossing from Iraq into the Islamic republic - only because a border guard of unknown nationality gestured for them to approach, the lone hiker to be released said Sunday.

In an interview broadcast Sunday morning with Christiane Amanpour on ABC's "This Week," Mr. Ahmadinejad said that the Iranian government "took a humanitarian measure and released one of the three individuals who entered our borders," so "I believe it would not be misplaced to ask that the U.S. government should make a humanitarian gesture and release the Iranians who were illegally arrested and detained here in the United States."

A senior Iranian prosecutor said Sunday that authorities will release a jailed American woman on $500,000 bail because of health problems, another sudden about-face by Iran in a case that has added to tension with the United States. The news came during a weekend of start-and-stop announcements about the release of Sarah Shourd, who was detained with two friends, Shane Bauer and Josh Fattal, along the Iran-Iraq border on July 31, 2009, and accused of spying.