Story highlights "These allegations are untrue," captive American's family says

Amir Hekmati's family says they last saw him in August

He is a former U.S. Marine who went to Iran to see relatives, they say

They say they stayed quiet at Iran's request

The family of an Iranian-American man held in Iran on spying charges says he was there to visit relatives and called the purported confession aired by Tehran "forced."

Amir Mirzaei Hekmati, a former U.S. Marine, was arrested in August while visiting his grandmother and other relatives, his family said. In a statement released Tuesday, they said they remained quiet about the arrest at the urging of Iranian officials, who promised his release.

"Amir's family was shocked by the recent broadcast aired on Iranian TV with false information and a forced confession," they said. "Amir has never had any affiliation with the CIA, and these allegations are untrue.

"Amir's family hopes that this misunderstanding can be resolved peacefully with Iran, and that Amir can be reunited with his family and friends in the U.S. who miss him dearly, and are praying for his safe return," they said.

Iran's semi-official Fars news agency reported Sunday that Hekmati had received language training and became an intelligence analyst in the Marines. It aired video showing what it called his confession, in which he appeared calm and collected, sitting in a quiet, well-furnished room as he spoke.

But Fars did not broadcast his full statement, and it was not clear what questions he had been asked.

The Hekmatis said their son served in the Marines from 2001 to 2005. After that he started his own linguistics company and contracted his services to the military as well as civilian businesses.

His military contracts included cultural competency training. He worked with troops at military bases to promote understanding of and positive communication with people of other cultures, his family said.

The family said he went to Iran in August after obtaining permission from the Iranian Interests Section of the Pakistani Embassy in Washington. The United States and Iran have no direct diplomatic relations.

"The Iranian government detained Amir on August 29, 2011, without any charges, and urged our family to remain silent with the promise of an eventual release," the family said.

In Washington, U.S. State Department spokeswoman Victoria Nuland told reporters Tuesday that Hekmati is being falsely accused, but had no further comment.