Donald Booth, US Special Envoy for Sudan and South Sudan, gave a major policy speech on US relations with both countries at the Atlantic Council in Washington on 9 October 2014. You can access the podcast and his written remarks titled "U.S. Policy on Sudan and South Sudan: The Way Forward" on the Atlantic Council website.
His remarks on South Sudan were a frank and hard hitting analysis of the failures in that country since independence. He emphasized the United States remains committed to helping the people of South Sudan. He was equally critical of the situation in Sudan but set down principles for a normalization of relations.