GENEVA -- A U.N. human rights expert accused the U.S. government on 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.

After a two-day "interactive dialogue" with U.S. officials at the United Nations in Geneva, Heyns said he was still waiting for a satisfactory reply.

"I don't think we have the full answer to the legal framework, we certainly don't have the answer to the accountability issues," he told reporters on the sidelines of a U.N. Human Rights Council meeting.