ISLAMABAD, Pakistan — Thousands of people gathered Saturday in the northwestern city Peshawar to protest American drone strikes inside Pakistani territory and vowed to stop NATO supply trucks unless the attacks stopped.

The protest rally was organized by Pakistan Tehreek-e-Insaf, the political party of the opposition leader Imran Khan, an outspoken critic of American drone strikes and the Pakistani military’s presence in the country’s border areas, where Taliban and Al Qaeda militants have long found a haven.

Addressing 10,000 to 13,000 flag-waving party workers and supporters from two allied political parties, Mr. Khan accused the United States of sabotaging peace talks with the Taliban. “There can be no peace unless drones are stopped,” he said.

Pakistani politicians denounce the attacks as a violation of the country’s sovereignty. Pakistani officials have regularly condemned the strikes in public while, in the past, endorsing them in private. But increasingly the drone campaign has strained relations between Pakistan and the United States.