A Marine veteran imprisoned in Iran has renounced his dual-citizenship with that country.

Amir Hekmati, an Iranian-American, former sergeant and veteran of the Iraq War, made the statement in a letter released by his family Tuesday. Iranian authorities arrested him while he visited relatives there more than three years ago and have held him ever since.

Initially charged with espionage — an accusation his family and U.S. authorities adamantly deny — Hekmati was sentenced to death. Iranian officials later changed the charges, but the one-time Marine has languished in one of the country's most infamous prisons, and in reportedly deplorable conditions, while negotiations over his freedom continue.

Through his family, which lives stateside, he also has accused officials in Washington and Tehran of using him as a bargaining chip in ongoing talks about Iran's nuclear program.

In a letter to the Iranian Interest Section in Washington, the closest thing the influential Middle East nation has to diplomatic relations with the U.S., Hekmati described his initial pride of his heritage and his shock at how his captors treated him. He recalls the painful moment when an Iranian authority described him as just "Iranian by name."

"Hence it has become very clear to me that those responsible [for my imprisonment] view Iranian-Americans not as citizens or even human beings, but as bargaining chips and tools for propaganda," Hekmati wrote. "Considering how little value the [Iranian] Ministry of Intelligence places on my Iranian citizenship and passport, I, too, place little value on them and inform you, effective immediately, that I formally renounce my Iranian citizenship and passport."

Hekmati's family, based in Michigan, released the letter along with more details about his captivity and a demand of deportation. According to them, he weathered 17 months of solitary confinement, was kept from sleep, has been cut off from his family and is fed little.

The more extreme charges accuse Iranian authorities of whipping his feet, using a Taser TASER on him, filling him with lithium with the express purpose of forcing him to suffer withdrawals and shackling him in a three-by-three foot cell, according to a document released by a family spokesman.

They also allegedly lied to him about his mother dying in an automobile accident and made him watch other prisoners undergo torture, the document states. Meanwhile, his father — back in the U.S. here — battles cancer.

Hekmati's plight has drawn the attention of past and present Marines. Many veterans undertook a symbolic hunger strike to raise awareness of the imprisoned Iranian-American's conditions late last year.

His local congressman also attempted to raise public interest in Hekmati earlier this year, setting aside a seat at President Barack Obama's State of the Union Address for the veteran.

Similar efforts are underway for another imprisoned Marine veteran: Austin Tice. Tice, who became a reporter, vanished while covering the civil war in Syria for multiple media outlets, filing award-winning stories along the way. His family launched a #FreeAustinTice campaign on social media last month.

Hekmati's family said he will never return to Iran once released. He continues to hold onto his Iranian background, but critiqued the government for using him as a political tool in his letter to authorities.

"My Iranian heritage and affinity for the Iranian people will always be a part of me, but I wish to have no ties to an organization that places so little value on my human rights and dignity and is willing to destroy an entire family for simple propaganda purposes," Hekmati wrote.