TEHRAN, Iran -- A former U.S. Marine convicted of criminal charges in Iran after being accused of working for the CIA will appeal for a new trial after already seeing his sentence reduced once, an Iranian news agency reported Sunday.

Amir Hekmati, a dual U.S.-Iranian citizen born in Arizona, was arrested in August 2011, then tried, convicted and sentenced to death for spying. However, Iran's Supreme Court annulled the death sentence after Hekmati appealed, ordering a retrial in 2012. The country's Revolutionary Court then overturned his conviction for espionage, instead charging him with "cooperating with hostile governments" and sentenced him to 10 years in prison.

Mahmoud Alizadeh Tabatabaei, Hekmati's lawyer, said he would appeal the 10-year prison sentence as well, according to a report by the semi-official ISNA news agency. ISNA quoted the lawyer saying the rehearing request comes over a possible mistake by the judge in the case and the "inconsistency" between Hekmati's alleged crime and its punishment. Iranian law allows for hearings after an appeals court decision for those reasons.

Tabatabaei said Hekmati has handed his request for rehearing to prison authorities.

Iranian prosecutors said Hekmati received special training and served at U.S. military bases in Iraq and Afghanistan before heading to Iran as a spy.

The Obama administration in November asked for Iran to free Hekmati and two other Americans believed held there, as relations recently have thawed between Washington and moderate President Hassan Rouhani. The call comes as world powers continue negotiations with Iran over its contested nuclear program.

His family, now in Michigan, says Hekmati is innocent and only went to Iran to visit his grandparents. The U.S. government repeatedly has denied the 31 year old is a spy.

Previously, Tabatabaei said he sought Hekmati's conditional freedom from Evin prison, north of the capital, Tehran. Hekmati has been behind bars since his arrest.

Conditional freedom could allow Hekmati to leave the country, depending on what a court decides. That could allow Hekmati to visit his father Ali Hekmati, a professor at Mott Community College in Flint, Michigan, who family members say has been diagnosed with terminal brain cancer and recently suffered a stroke.

Tabatabaei said a doctor treating Hekmati's father at a U.S. hospital has sent him a letter asking the ex-Marine's leave on bail to meet his ailing father.