Africa's newest nation, South Sudan, is in trouble. Less than a year after independence from Khartoum, the South and its much larger northern neighbour are confronting each other over oil reserves, borders and territory. Sporadic fighting has prompted mutual recrimination and talk of all-out war.HARDtalk’s Stephen Sackur speaks to South Sudan's foreign minister Nhial Deng Nhial. The African Union and the UN are pushing hard for a negotiated settlement, but is it already too late?