By Tim Cocks and Absoulave Massalatchi NIAMEY (Reuters) – Niger has asked the United States to start using armed drones against jihadist groups operating on the Mali border, raising the stakes in a counterinsurgency campaign jolted by a deadly ambush of allied U.S.-Nigerien forces. On Oct. 4, Islamist militants with sniper rifles and rocketpropelled grenades killed four U.S. soldiers and at least four of their Nigerien partners in an ambush that exposed the dangers of an expanding U.S. presence in the largely desert nation. “I asked them some weeks ago to arm them (the drones) and use them as needed,” Defence Minister Kalla Mountari told Reuters in an interview in his office.