A former U.S. Marine imprisoned in Iran has written to Iran's president saying he rejects any Iranian proposals to participate in a prisoner swap.

Amir Hekmati's family in Michigan released a copy of the letter Wednesday that he dictated to relatives on Jan. 2 via prison phone. Hekmati's Iranian lawyer sent the letter this week to President Hassan Rouhani, but it's not clear if he received it.

Hekmati, a dual U.S.-Iranian citizen, was arrested in 2011 and sentenced to death for spying. Authorities last year overturned that sentence and imprisoned him for 10 years.

U.S. officials say a prisoner swap has not been discussed.

Iranian Foreign Minister Mohammed Javad Zarif told reporters in Geneva that the Iranian judiciary found Hekmati guilty but is trying to help "on humanitarian grounds."