Two vehicles of US embassy officials were on Monday stopped in Pakistan's northwest tribal region, and pistols and automatic rifles were confiscated from them, a media report said.
The US embassy cars were stopped on the outskirts of Peshawar, capital of Khyber Pakhtunkhwa province, Xinhua reported.
Police said the US officials did not have a permit for carrying any of the weapons.
US consul general Mary Richard reached the site, and said the weapons can be seized but the foreign nationals should not be taken into custody.
The government of Khyber Pakhtunkhwa had issued new instructions to the provincial administration last week that diplomats and members of diplomatic missions cannot carry weapons unless given permission by the government.
Xinhua said the US diplomats had been detained in the past for trying to illegally enter Peshawar, where all foreigners are required to get special permission to visit.