Federal prosecutors have reached a tentative plea agreement with a former CIA officer accused of stealing hundreds of gold bars worth more than $40m from the US spy agency and hiding them in his basement, court records show.

David Rush and federal justice department prosecutors have a “plea agreement in principle”, the parties said in a Friday court filing. The parties also asked a judge to extend the 17 September deadline for three weeks through 8 October to allow them time to “resolve the matter prior to an indictment”.

“The parties need additional time to prepare the paperwork, including an agreed upon statement of facts,” assistant US attorney Raizza Ty and Rush’s attorney, Jessica Carmichael, wrote in the joint filing. “A pre-indictment resolution promotes the public interest by conserving government and judicial resources.”

There were no further details in the court filing about the working plea agreement.

Rush, a former executive service-level employee for the CIA, was fired after allegedly taking 303 bullion bars, each weighing 2.2lb (1kg) – and more than $2m in foreign currency – from his government office, according to an FBI affidavit. The search of his home in Virginia also turned up 35 luxury watches, many of them Rolex.

He was arrested on 19 May and charged with one count of stealing public money after allegedly falsifying his educational qualifications and military service to secure his job with the CIA. He also allegedly submitted fraudulent timecards to claim about $77,000 in compensation for military leave he wasn’t entitled to.

After his arrest, investigators discovered the full details of a fake classified program Rush had set up and through which he requested the gold bars and foreign money as “work-related expenses”.

He had also allegedly lied about his academic credentials and military background across multiple employment applications, including falsely claiming to have been a navy pilot.

Rush has been held in custody since his arrest after being deemed a flight risk. He had been a CIA agent for 17 years and served in the agency’s science and technology division.

The CIA hasn’t disclosed what his exact role entailed.