The embassy said the diplomat, Raymond Allen Davis, shot the men in self-defense and had diplomatic immunity from prosecution. Police in the eastern city of Lahore, where the shooting occurred, and senior law enforcement authorities "failed to observe their legal obligation to verify his status," and Davis's continued detention represented a "violation of international norms" and the Vienna conventions, the statement said.
"The diplomat had every reason to believe that the armed men meant him bodily harm," the embassy statement said. "Minutes earlier, the two men, who had criminal backgrounds, had robbed money and valuables at gunpoint from a Pakistani citizen in the same area."
Pakistani officials have said they are looking into whether Davis qualified for diplomatic immunity. But several Pakistani news reports, citing unnamed officials, have said they did not consider Davis a diplomat. The embassy statement said Davis was assigned to the embassy in Islamabad and was working under a diplomatic passport with a visa that expires in June 2012.
On Friday, Davis told a court in Lahore that he had killed the two Pakistani men in self-defense, saying the men had tried to rob him while he waited at a busy intersection in his car. A second consular vehicle that he summoned for help struck and killed a motorcyclist as it sped to the scene, police said.
A judge ordered the official held in custody for six days for further questioning.
Pakistani officials insisted Friday that the American would receive no special treatment while possible charges of murder and illegal weapons possession are investigated.
"No one will be allowed to breach the law in Pakistan," Interior Minister Rehman Malik told legislators. "The law will take its due course."
The incident has generated enormous media coverage in Pakistan and threatened to strain U.S. relations with the country, a key ally and recipient of U.S. assistance. The deaths are being widely depicted as an illustration of Americans' disregard for ordinary Pakistanis and as a test case of the unpopular central government's capacity to stand up to its U.S. sponsors.
Davis arrived in Pakistan in September 2009 as a "technical adviser" to the consulate in Lahore, according to sources who said his job was to assist in vetting visa applicants. His initial three-month diplomatic visa, listing his birth year as 1974 and a home address in Las Vegas, has been repeatedly extended at U.S. request since then.
The CIA has declined to comment on whether Davis worked for the agency, although Pakistani officials said they do not believe he is an intelligence agent. Under special budget provisions, the State Department has given diplomatic status to hundreds of temporary employees hired in recent years, some of them through contractors, to bolster the ranks of rapidly expanding embassies in both Pakistan and Afghanistan.