Aerial reconnaissance and attack drones have had a liberating effect on U.S. military forces, but they are deeply hated by many people and their overuse could jeopardize Washington's broader objectives, retired General Stanley McChrystal said on Monday.

McChrystal, who authored the U.S. counterinsurgency strategy in Afghanistan, said use of drones had enabled him to carry out missions with smaller groups of special operations forces because the "eye in the sky" provided backup security.

"What scares me about drone strikes is how they are perceived around the world," he said in an interview. "The resentment created by American use of unmanned strikes ... is much greater than the average American appreciates. They are hated on a visceral level, even by people who've never seen one or seen the effects of one."