Obama to wade into South Sudan peace drive

US President Barack Obama will on Monday try to build African support for tough action against South Sudan's warring leaders if they reject an August peace ultimatum, US officials said. Obama will meet with leaders from Ethiopia, Kenya and Uganda as well as Sudanese Foreign Minister Ibrahim Ghandour in Addis Ababa to try and build a collective front to end the 19-month-old civil war in the world's youngest nation. Signalling a deeper commitment to ending violence that has killed tens o