GENEVA (AP) — A U.N. human rights expert accused the U.S. government Wednesday of sidestepping his questions on its use of armed drones to carry out targeted killings overseas.

Christof Heyns, the U.N.’s independent investigator on extrajudicial killings, had asked the United States to lay out the legal basis and accountability procedures for the use of armed drones. He also wanted the U.S. to publish figures on the number of civilians killed in drone strikes against suspected terror leaders in Afghanistan, Pakistan, Yemen and elsewhere.