The U.S. delegation chief to South Sudan's upcoming independence celebration says the situation remains tense there despite the African country's successful split into two nations.
Susan Rice, U.S. ambassador to the U.N., called it a "fragile and fraught moment."
She said the northern and southern governments must resolve issues related to the resource-rich area of Abyei and other border areas. There are also questions linked to citizenship and oil.
Rice said Thursday that failure on these fronts could cause economic shock or social upheaval.
She said Sudan's government must settle all disputes in order to be removed from the U.S. state sponsors of terrorism list.
Still, Rice called Saturday's independence celebration very significant after two decades of civil war. Fighting ended in 2005. The south voted for independence in January.