Jonathan Pollard, whose release was demanded by Israel as the price of peace, is a former US navy analyst serving a life term for spying for Israel.
Israel has repeatedly requested that the US free Pollard, who was arrested in 1985 and convicted on espionage charges two years later. He has been in prison in North Carolina.
To facilitate his release, Israel gave him citizenship in 1996 and in May formally acknowledged that he had spied for the Israelis.
Pollard (43) was convicted of giving Israel top secret documents on PLO installations in Iraq and Tunis for $50,000. He had been recruited by a branch of the Israeli Defence Ministry.
Israel initially denied any link to Pollard but recently has embraced him, with the Israeli Prime Minister, Mr Benjamin Netanyahu, recently sending him a note saying: "The state of Israel will go on working, tirelessly and dauntlessly, to bring you home."
Pollard's wife, Anne, was sentenced to five years in prison. She emigrated to Israel when she was released.
The Pollards, however, have since divorced and Jonathan Pollard has remarried.
Despite Israel's efforts, the US has been furious that an ally recruited a spy in its midst and has repeatedly balked at reducing his sentence.
In July 1996 President Clinton refused Pollard clemency at the request of US intelligence services.
Mr Netanyahu brought the subject up in a meeting with Mr Clinton in early October, but was rebuffed.