It said that "following careful consideration, the department has restricted the number of sites in the U.K. at which UPS Ltd. are permitted to screen air cargo until it has satisfied current security requirements."
The department said it could not give details of the sites for security reasons.
UPS could not immediately be reached for comment. The vulnerability of air cargo to terrorist attacks is a major worry for international security agencies.
Last October, two bombs were sent disguised in toner cartridges on cargo flights from Yemen bound for the United States. One was discovered at a FedEx cargo facility in Dubai, the other at a UPS depot in England.
Officials said the bombs were viable and could have exploded in mid-flight. Al-Qaida was blamed for the plot.
In March, someone shipped a hoax bomb -- which had a timer, wires and a detonator -- to Turkey via the UPS office in London.