A permanent U.S. resident who has been imprisoned in Iran for more than a year has told his representing attorney that the Iranian government is demanding a ransom in exchange for his release, according to the Washington Examiner.

Nizar Zakka, a Lebanese citizen and permanent resident of the United States, said Iranian officials told him in April it would take as much as $2 billion for his release from prison. In September, Iranian officials lowered that amount to $4 million, but he would remain in prison until the payment was made.

"This is a grave breach of, among [other international laws and treaties], the Geneva Conventions against hostage-taking," his lawyer, Jason Poblete, said on Tuesday. "Iran is using Nizar, other Americans and dual nationals, as political chattel to exact concessions from the U.S. and other powers."

Since Zakka was captured last fall, Poblete says his client has been psychologically tortured and subjected to inhumane and degrading treatment.

"On behalf of Nizar, we request that all be done by the U.S. and other governments to secure his unconditional release from captivity on humanitarian grounds," Poblete said. "Nizar is extremely weak and getting sicker."