Israel's prime minister made a public appeal Tuesday for the freedom of an American who spied for Israel, asking in a letter to President Barack Obama for clemency after the spy has spent 25 years behind bars.

The case of Jonathan Pollard "unites us all," Benjamin Netanyahu told his parliament, before reading the letter.

The request comes at a low point in Israel-U.S. relations over stalemated Israeli-Palestinian peace talks. A deal that would have given Israel advanced warplanes and political backing in exchange for an extension of a slowdown in settlement construction to restart peace talks, but it fell through.

In Washington, State Department spokesman P.J. Crowley said the administration would review the request.

With relations with the U.S. strained over the lack of progress in peace efforts, it appeared unlikely it would be approved. Previous Israeli appeals have been met coolly.

Pollard, now 56, was turned away from the Israeli Embassy in Washington in 1985 with U.S. authorities close behind. He was arrested and sentenced to life in prison for passing classified information to Israel about Iraq and other subjects.