Sudan is battling the Sudan People's Liberation Movement-North, a branch of a guerrilla movement that has fought various regimes in Khartoum for decades. SPLM-North was once part of South Sudan's ruling party during a long civil war between Sudan's north and south.
South Sudan became the world's newest country last July. Citing security concerns, Khartoum has refused to allow humanitarian aid agencies into the region.
U.S. Deputy Secretary of State William Burns said Monday that aid groups must be allowed into Blue Nile and South Kordofan to avert a crisis. He said it was extremely important that humanitarian concerns be addressed.
Da Silva said Khartoum was willing to allow humanitarian access to the two states "under a certain set of conditions which we have not accepted." He said Khartoum would not allow Sudanese citizens to be involved in the operations.
Da Silva said the World Food Program was planning for a "worst-case scenario" to assist from 300,000 to 500,000 refugees in South Sudan should the talks fail.
The main catalyst of the potential influx is a deepening food crisis spurred by erratic rains in Sudan and instability due to the violence.
But according to WFP, things are not much better in South Sudan. In addition to the refugees along the border, an estimated 120,000 people have been affected by recent tribal violence in the volatile state of Jonglei. And WFP estimates that the country's cereal deficit will be at least 440,900 tons in 2012.
