WASHINGTON (AFP) - A leading US space scientist pleaded guilty Wednesday to attempted espionage for selling classified material to a US undercover agent he thought was an Israeli spy, the Justice Department said. Stewart Nozette, 54, entered the guilty plea as part of a deal with prosecutors that will result in a 13 year prison sentence if approved by a judge, sparing him a possible sentence of life in prison. Nozette agreed to provide classified information from his top-secret work as a govt scientist after meeting an undercover FBI agent who persuaded him he was an agent for Mossad. "Happy to be of assistance," Nozette told the agent, according to a Justice Department account.