"The American Embassy in Islamabad has received threat information regarding possible terrorist attacks against locations in Islamabad in late December, especially during the Christmas and New Year's holiday period," the embassy said.
"Possible targets include places of worship and shopping centres," it said.
The embassy in a statement last week advised American citizens to exercise particular caution during the holiday season and at holiday festivals or events.
On August 28, the US issued travel warning for Pakistan and a worldwide travel alert on November 23.
American government personnel are under additional movement restrictions.