The State Department is denying a report that the U.S. is proposing an exchange of Iranian prisoners in the U.S. for a former American Marine currently in prison in Iran.

The report was carried by Iran's semi-official news agency, quoting a lawyer for Amir Hekmati.

The State Department says it's not true -- and it's calling again for Hekmati's release on humanitarian grounds.

Hekmati, a dual U.S.-Iranian citizen born in Arizona, was arrested in August 2011 and sentenced to death for spying. Earlier this year, authorities overturned his death sentence and reduced his sentence to 10 years in prison.

Hekmati told his family in Michigan by phone on Dec. 16 that he was beginning a hunger strike and dictated a letter asking President Obama not to forget him as negotiations proceed with Iran over its nuclear activities.