The Associated Press reports: The Pakistani military blocked a convoy carrying thousands of Pakistanis and a small contingent of U.S. anti-war activists from entering a lawless tribal region along the border with Afghanistan on Sunday to protest American drone strikes.

The group, led by cricket star turned politician Imran Khan and his political party, was turned back just miles from the border of South Waziristan. After an hour of fruitless negotiations, Khan announced that the caravan would backtrack to the city of Tank, about 15 kilometers (nine miles) away. There, he delivered a speech to the crowd of about 10,000.

Khan has harshly criticized the Pakistani government’s cooperation with Washington in the fight against Islamist militants. He has been especially outspoken against U.S. drone strikes targeting militants and has argued that the country’s alliance with Washington is the main reason Pakistan is facing a homegrown Taliban insurgency. He has suggested before that militant activity in Pakistan’s tribal areas will dissipate when the U.S. ends the war across the border in Afghanistan.