This undated file photo shows Amir Hekmati, a U.S. Marine veteran who has been held in Iran since August 2011 and accused by Tehran of being a CIA spy. (Hekmati family via FreeAmir.org/Associated Press)

Amir Hekmati, a U.S. Marine veteran held by Iran since August 2011, has begun a hunger strike to protest his captivity, his family says.

The family was informed of his plans Tuesday, according to the Associated Press. Hekmati, a dual citizen of Iran and the United States, was captured while visiting his grandmother in Iran, his family says. Tehran has accused him of being a CIA spy, something Hekmati and the U.S. government deny.

The news comes as Cuba, a close partner of Iran’s, released Alan Gross, 65, an American contractor with the U.S. Agency for International Development who was detained in December 2009 while setting up illegal Internet access in the island nation. He was later sentenced to 15 years of confinement for espionage. The United States protested his treatment, but Gross languished as a prisoner for five years.

Hekmati remains in prison. He initially was convicted of espionage and sentenced to death. He appealed the case, leading Tehran’s court system to overturn it. He was then charged with “cooperating with hostile governments” and sentenced to 10 years in prison.

According to Foreign Policy, Gross’s family had sought his release, noting that his daughter and mother both have cancer. That has some similarities to Hekmati’s case: The Marine’s family says his father has brain cancer, and also had a stroke.

A Facebook page devoted to freeing Hekmati posted a letter on Wednesday from Hekmati to President Obama asking him to help end the “nightmare” he has been living. It was dictated from prison on Monday:

Hekmati, who served as an infantryman from 2001 to 2005, says in the letter that his imprisonment has included time in solitary confinement. He is deeply concerned that his release is tied to U.S. negotiations with Iran over its nuclear program.

“I ask that you not forget me, Mr. President,” Hekmati said. “I understand there will be additional dialogue this week on the nuclear subject. I ask that you make it clear that my case is unrelated and should be resolved independent of your talks. I ask that your team impress on Iranian officials that more than three years without resolution is simply too long.”

Hekmati adds that he is aware that diplomatic relations between Washington and Tehran are delicate, “but I should not fall victim to it.”