The man identified as William Johns, who worked as a security trainer at the US embassy in Islamabad, was detained earlier today at the Benazir Bhutto International Airport while carrying 15 bullets of 9 mm calibre and a magazine.
After initial investigation by Airport Security Force, he was handed over to police.
Abid Ahmad, a police official at Airport Police Station, told PTI that a case was registered against Johns for carrying illegal weapons.
“He was presented before the judge who set him free on bail,” said Ahmad.
The accused had confessed to carrying the ammunition by mistake. He was planning to board a Dubai-bound Etihad Airlines flight on way to the US.
It is the second incident of arrest of a US embassy official with ammunition.
In May, Joel Cox, an FBI agent, was arrested with pistol bullets from Karachi airport.
He was later set free when the US embassy showed a letter proving that he was authorised to carry weapons.
US relations with Pakistan have been fraught since CIA contractor Raymond Davis shot two men dead in Lahore in 2011.
Davis was later released after paying USD 2 million in blood money to the relatives of the victims.