They charge that Sudan's delay in implementing a three-party plan to deliver food to civilians in rebel-held areas shows Khartoum is not willing to resolve the crisis, the Sudan Tribune reported.
Malik Agar, chairman of the Sudan People's Liberation Movement-North, led a delegation from Addis Ababa, Ethiopia, to Washington, D.C., where he was expected to meet with a number of U.S. State Department officials, including Princeton Lyman, the department's special envoy to Sudan.
Agar was accompanied by SPLM-N Vice Chairman Abdel Aziz al-Hilu and Secretary-General Yasir Arman.
The trio want the United States to support a comprehensive process for Sudan that goes beyond the "Two Areas" protocol Sudan agreed to in a peace agreement with the rebel group in 2005.
Sudan has said it wants to include traditional leaders as well as civil society groups in South Kordofan and Blue Nile in peace talks. It wants to exclude the rebel group from the talks because it says Arman and al-Hilu are not from the Two Areas.
The SPLM-N says the inclusion of the other groups in the negotiations is an "empty public relations gesture."
The rebels say the government of Omar Bashir has not worked seriously to reach a negotiated political settlement to the conflict and that Khartoum has not allowed access by humanitarian organizations to areas held by SPLM-N.