The man, Nahum Manbar, was arrested in 1997 and later indicted and convicted for aiding an enemy of the State of Israel and for selling potentially harmful information to an enemy state.
The indictment claimed that during the 1980s, Manbar, who had business connections in Iran, used them to supply enemy agents with sensitive information and equipment.
Manbar was sentenced to 16 years in prison. He later appealed to the Supreme Court, which rejected his appeal, and is currently serving his sentence in the Nitzan Prison in Ramla.
The prison parole board is scheduled to convene later this week to discuss the possibility of deducting a third of his sentence.
The prison parole board is made up of a retired judge, two social workers, and a representative of the Israel Prison Service, and while the head of security in the Defense Ministry is not opposed to Manbar's release, the Shin Bet and the Mossad are against it.
A source in the Israeli Prison Service said Sunday that Manbar was considered a well-behaved prisoner, who showed no disciplinary problems. He is not in solitary confinement, and had recently been placed on the prison's maintenance crew and been authorized vacations.
Manbar's attorney, Avi Richtman, had been trying to get the Tel Aviv district attorney, Rachel Shiber, to support his client's appeal to the parole board, since any support shown by the State Prosecutor's Office will carry substantial weight with the board. .
Should the parole board decide to parole Manbar, he may be released from prison in the near future.
Yoram Yarkoni contributed to this article