The warning comes as Chad, Sudan and the Central African Republic signed a deal [at Africa-France summit] not to support rebels attacking each other's neighbouring territory.
African Union head, Ghana's President John Kufuor, said they seemed ready to agree to an AU/UN border peace force.
"They seem to be ready to accept a beefed-up force from the African Union and the United Nations to take control of the borders among them," Mr Kufuor told reporters at the French-African summit in Cannes where the declaration was signed.
BBC World Service broadcasts to Juba in Southern Sudan and surrounding areas in Arabic on 90.0 FM and in English on 88.2 FM. In Northern Sudan: Khartoum 91.0 FM, Al Ubayyid 91.0 FM, Port Sudan 91.0 FM and Wad Madani 91.5 FM.
“Violence will bring no victory. For the sake of the Darfur civilians, all parties to the conflict have to stop resorting to violence. This is the absolute priority.” - Luis Moreno-Ocampo, Prosecutor of the International Criminal Court, 05 June 2009
"APPREHENSION" by Rob Rooker. Painted on a wall in Maridi, Sudan. The image is of a young Nuer boy looking up among a crowd of people. Click on image for more details. Cards & prints of Rob's paintings can be purchased online at Imagekind.com