Iran said Saturday morning it has put on hold the release of one of the three U.S. hikers in its custody, reversing an earlier announcement on the American woman's release.

Foreign Ministry Spokesman Ramin Mehmanparast said on the previous day that it was decided that "this lady (Sarah Shourd) to be released soon to join her family."

However, an official from the information center of Iran's presidential office said Saturday that "the release of an American spy which was set for Saturday ... was postponed."

"The details (of postponement) will be issued later," Mohammad Hassan Salehimaram was quoted by official IRNA news agency as saying.

Tehran Prosecutor General Abbas Jafari-Dolatabadi told Press TV that judicial proceedings in the defendant's case have not been completed.

"Because the legal procedure for Sarah Shourd's case is not finished, her release is cancelled," he said, without saying when the American woman would be freed.

But in an email sent to Xinhua by spokesman Bak Sahraei of the Iranian Mission to the UN on Thursday, the release will be "very soon."

Shourd and the other two U.S. hikers, Josh Fattal and Shane Bauer, were arrested in Iran on July 31 last year after illegally entering the country from its western borders. They were charged with espionage in November, but Washington said the charges was unfounded and all of them should be freed.

In May, the mothers of the three Americans were allowed by the Iranian government to meet them in Tehran.

The U.S. State Department on Thursday urged Iran to release all three hikers after Tehran announced it will release one of them on Saturday.

"If this turns out to be true, this is terrific news. The hikers' release is long overdue," said department spokesman Mark Toner.

But Toner urged Iran to release all three hikers instead of only one, saying the U.S. government has called for their release "on humanitarian grounds for many, many months."