Human rights groups said they uncovered evidence that Sudanese airstrikes on the population of South Kordofan left crop devastation, displacements and scores of civilians dead in their wake.
South Kordofan state borders South Sudan, which became an independent country in July as part of a comprehensive peace deal in 2005 that ended Sudan's civil war, one of the bloodiest on record.
Sudan blames rebel fighters with the Sudan People's Liberation Army for much of the violence though the United Nations said there is evidence to suggest much of the violence is ethnically motivated.
Ahmed Mohamed Haroun, governor of South Kordofan, said he was working to make sure conditions in the area were favorable for the return of displaced citizens, the state-run Sudan News Agency reports.
The Sudanese government discounts many of the claims regarding ethnic violence in South Kordofan, saying the situation there is calm.
But Victoria Nuland, a spokeswoman for the U.S. State Department, said in a statement both sides need to respect the rule of law.
"The United States calls on both sides to allow unfettered humanitarian access to affected populations in South Kordofan and urges the parties to resume formal negotiations to reach a permanent cessation of hostilities and a political settlement," she added.