Iran on Tuesday put on trial an American man of Iranian descent accused of spying for the US CIA.

"I am Amir Mirzai Hekmati"

Iran on Tuesday put on trial an American man of Iranian descent accused of spying for the US Central Intelligence Agency, Fars news agency reported.

"The first hearing in the trial of Amir Mirzai Hekmati, recently arrested for spying for the United States, started Tuesday" in a closed Tehran court, Fars reported.

Hekmati, a 28-year-old former US Marine born in the United States to an Iranian immigrant family, was shown on Iranian state television mid-December saying in fluent Farsi and English that he was a CIA operative sent to infiltrate the Iranian intelligence ministry.

Hekmati's trial opened against a backdrop of heightened tensions by Washington against Tehran.

The United States is leading a Western push to ratchet up sanctions on Iran over its peaceful nuclear program.

Fars said Hekmati's trial started with the prosecutor saying Hekmati was charged with cooperating "with the hostile US government and the US espionage services of the CIA."

Hekmati had admitted to trying to infiltrate Iran's intelligence services for the CIA, as well as to having a first interview with the CIA in 2009 and being trained for five months before being sent to Iraq, where he said he spent nine months.

After Iraq, the CIA hired him -- on a promised payment of $500,000 -- to infiltrate Iran.

"I was fooled by the US intelligence services. Even though I entered Iran with the mission of infiltrating the Iranian intelligence services to become a source of information for the CIA," Fars quoted Hekmati as saying.

"I had the intention of living in Iran and of not returning to the United States," he allegedly claimed.

Iran's intelligence ministry said Hekmati's cover was blown by Iranian agents who spotted him at the US-run Bagram base in Afghanistan.

The judge handling the trial, Abolghasem Salavti, said he would deliver his verdict after hearing the defense lawyer's counter-argument.

Espionage carries a potential death penalty in Iran.