DETROIT -- A former U.S. Marine held in Iran describes the miserable prison conditions he has endured in a new letter to Secretary of State John Kerry.
Amir Hekmati says Tehran is holding him hostage for use in a possible prisoner exchange, according to the letter addressed to Kerry and published by Britain's Guardian newspaper on Wednesday.
Hekmati has been detained on what the U.S. says are false espionage charges.
Family spokesman Greg Romano told The Associated Press on Wednesday that Hekmati's sister, Sarah, authenticated the letter. She says the handwriting is her brother's, as is the letter's tone.
The AP has sent an email seeking comment from the State Department.
The Guardian says it obtained the letter after it was smuggled out of jail.
