A former US government space scientist has pleaded guilty to one count of attempted espionage for trying to sell classified information to an undercover FBI agent posing as an Israeli spy.

During an appearance in federal court, Stewart David Nozette admitted trying to provide Israel with top-secret information about satellites, early warning systems, ways of retaliating against large-scale attacks, communications intelligence information and major elements of defence strategy.

Both the justice department and Nozette's lawyers have agreed to a sentence of 13 years in prison, with credit for two years Nozette has already spent behind bars. US district judge Paul Friedman said he was prepared to accept the deal, pending Nozette's co-operation with prosecutors, a procedure expected to last into November.

Appearing in court in a prison jumpsuit, Nozette said he understood the charge to which he was pleading. He could have been sentenced to death had he been convicted of all four counts of attempted espionage that he faced.

Just before his arrest, Nozette told an undercover FBI agent in the October 2009 sting operation the secrets he was passing to Israel had cost the US government between $200m and almost $1bn, according to newly filed court papers in the case.

"So I tell you … theoretically I should charge you certainly, you know, at most 1%", the court papers quoted Nozette as telling the agent.

In the conversation at the Mayflower Hotel in downtown Washington on 19 October, Nozette told the undercover agent: "I've crossed the Rubicon … I've made a career choice," and then, according to the papers, he laughed.

"The cost to the US government was $200m," Nozette is quoted as saying. "And then that's not including the launching of it … Integrating the satellites – that probably brings it to almost a billion dollars."

Nozette had high-level security clearances during decades of government work on science and space projects at Nasa, the energy department and the National Space Council in George Bush Sr's White House. He has a doctorate in planetary sciences from MIT, and was known primarily as a defence technologist who had worked on the Reagan-era missile defence shield effort formally called the Strategic Defence Initiative. He also helped discover evidence of water on the moon.

Because Nozette had access to such high-level information, including about the nation's nuclear missile programme, the attorney general, Eric Holder, ordered special communications restrictions placed on him in jail.

During a hearing after his arrest, the prosecutor played a video from the 2009 sting in which Nozette lounged on a hotel room couch, eating and laughing with the undercover agent. He discussed the possibility of having to flee the country if he came under scrutiny.