Updated at 9:14 a.m. ET
(AP) TEHRAN, Iran - Iran's Supreme Court has ordered the retrial of an ex-U.S. Marine who was sentenced to death on charges of working for the CIA, a news agency reported Monday.
The case has added even more tension to U.S.-Iran relations, as Washington and its allies press ahead with sanctions over Iran's contentious nuclear development program, and Iran threatens punishing retaliation if it is attacked.
Amir Hekmati, 28, was sentenced to death in January, the first American to receive a death penalty since the 1979 Islamic Revolution in Iran. Hekmati was born in Arizona. His parents are of Iranian origin.
Iran accuses Hekmati of receiving special training while serving at U.S. military bases in Iraq and Afghanistan before heading to Iran for an intelligence mission.
In December, Iran broadcast a video on state television in which Hekmati was shown delivering a purported confession, in which he said he was part of a plot to infiltrate Iran's intelligence agency.
The U.S. government has denied the charges against Hekmati.
On Monday, the semiofficial Isna news agency said the case would be retried.
The report quoted state prosecutor Gholam Hossein Mohseni Ejehei as saying, "There was an appeal on his verdict. The Supreme Court found shortcomings in the case and sent it for review by an equivalent branch" of in the court system.
The report did not elaborate.
Last month Hekmati's mother visited him in prison and met with Iranian officials. Some saw this as a sign that Iran might show moderation in the case.
A previous incident involving Americans in Iran was resolved, but only after two years.
In 2009, three U.S. citizens were detained along the Iraq border. The three said they crossed the border unintentionally during a hike. They, too, were charged with espionage, but there were no specific allegations of CIA ties and training as in the case of Hekmati.
The three were sent to prison. One was released for medical reasons and the other two were freed last September, in deals involving bail payments brokered by Oman, which has good relations with both Iran and the U.S.