WASHINGTON — Two members of Congress and the family of a former Marine now detained in Iran are calling for his freedom as he completes 1,000 days in prison on spying charges.

Iran arrested Amir Hekmati in August 2011 while he was on a trip to visit his grandmothers in Tehran. Hekmati is a dual US-Iranian citizen born in the US.

His sister and brother-in-law and Reps. Dan Kildee and Jim McGovern held an observance near the White House Monday and pressed Iran to release him.

Hekmati’s sister, Sarah, said their father developed brain cancer and, quote, “is fighting his body to hold on so he can feel his son in his arms again.”

Kildee said international nuclear talks with Iran could provide an opportunity for Hekmati’s release.

In April, an Iranian court overturned the death sentence given to Hekmati on charges of spying for the CIA, instead sentencing him to several years in prison.

Iranian prosecutors said Hekmati received special training and served at US military bases in Iraq and Afghanistan before heading to Iran as a spy. Hekmati’s family and the US government repeatedly has denied the 31 year old is a spy, instead saying he traveled to Iran to visit his grandmother.

Iran’s Supreme Court annulled the death sentence after Hekmati appealed, ordering a retrial in 2012. The country’s Revolutionary Court then overturned his conviction for espionage, his lawyer Mahmoud Alizadeh Tabatabaei told The Associated Press. Instead, it charged him with “cooperating with hostile governments” and sentenced him to 10 years in prison, Tabatabaei said.

Iran’s Appeals Court “recently” upheld the verdict, the lawyer said, a decision that is final.

Tabatabaei said he is seeking Hekmati’s conditional freedom from Evin prison, north of the capital, Tehran. Hekmati has been behind bars since his arrest.

“According to law, if someone serves one-third of his conviction period and within that time, shows an acceptable behavior in jail, he can be entitled to conditional freedom,” Tabatabaei said. “One-third of his imprisonment will end around September and October.”

Conditional freedom could allow Hekmati to leave the country, depending on what a court decides. That could allow Hekmati to visit his father Ali Hekmati, a professor at Mott Community College in Flint, Michigan, who family members say has been diagnosed with terminal brain cancer and recently suffered a stroke.

The Obama administration in November asked for Iran to free Hekmati and two other Americans believed held there, as relations recently have thawed between Washington and moderate President Hassan Rouhani. The call comes as world powers continue negotiations with Iran over its contested nuclear program.

Kildee, a Flint Democrat who represents Hekmati and his family in Congress and has worked to free him, said in a statement last month that releasing him would be “a tangible demonstration by Iran that it is serious about rejoining the global community.”

“He is innocent and has committed no crime,” Kildee said. “He is an American citizen who, with the permission of the Iranian government, traveled to Iran to simply visit his grandmother for the first time. He has been wrongfully imprisoned for 956 days.”

Tabatabaei said he hadn’t met face to face with Hekmati, but remained “constantly in contact with him.”

“His morale is good,” the lawyer said.

Copyright 2014 The Associated Press.