WASHINGTON — An American jailed in Pakistan for the fatal shooting of two armed men was secretly working for the CIA when he was arrested, a disclosure likely to further frustrate U.S. government efforts to free the man and strain relations between two countries.

Raymond Allen Davis, 36, had been working as a CIA security contractor and living in a Lahore safe house, according to former and current U.S. officials, who spoke on condition of anonymity.

Davis, a former Special Forces soldier who left the military in 2003, shot the men in what he described as an attempted armed robbery in the eastern city of Lahore as they approached him on a motorcycle. A third Pakistani, a bystander, died when a car rushing to help Davis struck him. Davis was carrying a Glock handgun, a pocket telescope and papers with different identifications.

Meanwhile, the Obama administration insisted anew Monday that Davis had diplomatic immunity and must be set free. i

In a conference call with reporters shortly after details of Davis’ employment were reported, senior State Department officials repeated the administration’s stance that he is an accredited member of the technical and administrative staff of the U.S. Embassy in Islamabad.