There appeared to be no sign of a rapprochement between the central players in the crisis : President Salva Kiir, an ethnic Dinka, and former vice president Riek Machar, who is a Nuer, as the ethnic killings threaten to overwhelm U.N., U.S. and African efforts to end the violence. In telephone calls Tuesday to Kiir and Machar, Secretary of State John F. Kerry urged them “to accept a cessation of hostilities and begin mediated talks,” State Department spokeswoman Jen Psaki said. The United States has been the primary international backer of South Sudan since its 2011 independence from Sudan. The U.S. Africa Command moved about 50 Marines to neighboring Uganda, better positioning them to take action to protect U.S. facilities and personnel, if needed. The Marines were part of a 150-strong contingent deployed Monday from their base in Spain, along with transport and refueling aircraft, to Djibouti, on the […]