Quoting US and international aid officials, the Washington Post Sunday said Pakistani authorities are denying permission to US embassy employees from visiting Peshawar.
The staff was proceeding to attend meetings or replace workers at the American consulate in Peshawar. Most Pakistanis view the Peshawar American consulate as a front for CIA operations.
"The widely publicised episodes in Peshawar threaten to become another flash point in a frayed bilateral relationship that US officials had hoped was improving," the report said.
After the killing of Al Qaeda chief Osama bin Laden by US commandos and the earlier gunning down of two Pakistanis by a CIA contractor in Lahore in January, Pakistan expelled more than 100 US army trainers.
In retaliation, the Obama administration stopped $800 million in aid to the Pakistani military.
The Washington Post quoted US officials as saying that their embassy notified Pakistani police that their employees were driving from Islamabad to Peshawar and should be escorted from the highway into the city.
On four occasions, the employees were turned away at the toll booth for lacking 'No Objection Certificates', which are issued by the Interior Ministry but also involve approvals from intelligence agencies, it said.
According to US officials, they have an agreement that diplomats can travel between embassy and consular posts without permits as NOCs can take more than a week.
Pakistani officials have said the requirement for permits was never waived and applies to all foreigners.
The refusal to the US embassy staff to enter Peshawar became a sort of media spectacle on all four occasions.
"Each time American vehicles were turned away from toll booths, television cameras were there," the report said.
Cut up with the Pakistani action, a US official has been quoted as saying: "This is not a constructive way to rebuild the relationship."