US: Iran Threatens Family of Nuclear Defector Shahram Amiri

June 28, 2010— -- This story has been updated.

The Iranian government has threatened to harm the family of a nuclear scientist who defected to the U.S. and helped provide crucial details about Iran's burgeoning weapons program unless he returns home, according to people in the intelligence community briefed by the CIA.

The high-stakes spy saga is being played out online, where both the Iranian intelligence agency and the CIA have posted dueling videos of the scientist. In one video, he claims the U.S. kidnapped him, in the other he says he is happy to be in the U.S.

Behind the scenes, the situation has become so grave that American officials fear Amiri could re-defect, according to the people briefed on the situation. A full report on the case will be broadcast Monday on ABC's "World News with Diane Sawyer" and "Nightline."

At the center of the intrigue is Shahram Amiri, an Iranian nuclear scientist, who officials say operated within Iran as a key CIA spy for several years before his defection.

Amiri apparently provided crucial information, though his precise role in U.S. intelligence gathering remains unclear. Former and current intelligence officials told ABC News that Amiri confirmed the existence of a secret underground enrichment facility near Qom and also described him as a key source in the conclusions of the 2007 National Intelligence Estimate, which found that Iran had suspended its nuclear weaponization program. Initially, before Amiri defected back to Iran, the same officials told ABC News that Amiri's information had contradicted the 2007 NIE finding, but further reporting indicates that was an incorrect interpretation.

CIA director Leon Panetta told ABC News yesterday on This Week that the CIA no longer believes the conclusions of the 2007 NIE, saying that Tehran continues "to work on designs" for a nuclear weapon.

"I think they continue to develop their know-how," Panetta said. "They continue to develop their nuclear capability."

CIA officials pushed for Amiri to flee the country out of fear that his disclosures might expose him to Tehran as a spy.

Amiri vanished last year during a pilgrimage to Saudi Arabia. The Iranian government claimed then that their scientist, a professor at Tehran's Malek Ashtar University, had been kidnapped by the CIA. In fact, say U.S. officials, the CIA, with the help of the Saudi government, whisked Amiri to the U.S., where he was to permanently resettle.