GENEVA (Reuters) – The U.N. human rights office on Tuesday called on the U.S. state of Alabama to halt its first planned execution of a prisoner by nitrogen gas asphyxiation this month, saying it could amount to torture and violate U.S. commitments under international law. Kenneth Smith, convicted for a murder-for-hire committed in 1988, is scheduled to be executed in Alabama on Jan. 25 using the method, in which execution officials will bind a mask to his face connected to a cylinder of nitrogen intended to deprive him of oxygen. “We have serious concerns that Smith’s execution in these circu…