More than 30,000 Islamists have rallied against the U.S. in the Pakistani city of Lahore following NATO airstrikes last month that killed 24 Pakistani soldiers.
Sunday's protest was organized by Jamaat-ud-Dawa, widely believed to be a front group for the banned Lashkar-e-Taiba militant organization.
Hafiz Saeed, the head of Jammat-ud-Dawa, demanded Pakistan cut off ties with the U.S., which has provided billions of dollars to Islamabad over the past decade to fight Islamist militants.
The U.S. has expressed its condolences for the NATO attack that killed the Pakistani soldiers at two army posts along the Afghan border on Nov. 26.
Many Pakistanis are still angry over the attack, which the Pakistani military has claimed was deliberate.