"The African Union has already stated that it could not continue in Darfur so, if it is unable to pursue its assignment beyond September 30, then they have to leave before this date," Foreign Ministry spokesman Jamal Ibrahim said.
"At the same time, they have no right to transfer this assignment to the United Nations or any other party. This right rests with the government of Sudan.
"Sudan will proceed with the implementation of the Darfur peace agreement according to its own plan to restore peace and stability in the region.
"This plan has already been lodged with the UN Secretary General (Kofi Annan) but it has not been well considered.”
The Sudanese plan provides for the deployment of some 10,000 government troops in Darfur. Reinforcements have already been sent to North Darfur, where renewed fighting broke out over the past week.
The Sudanese government had already rejected a UN Security Council resolution passed on Thursday which calls for the deployment of more than 20,000 UN peacekeepers to take over from the embattled 7,000-strong AU contingent.
Khartoum submitted plans to the UN for the deployment of its own troops to replace AU monitors in Darfur, but the idea was rejected by the United States and angered rebel movements.
Sudanese government troops "aren't considered neutral," Washington's top Africa envoy - Jendayi Frazer, the assistant secretary of state for African affairs - said last month.
Government troops have already started massing in some parts of Darfur and AU officials reported renewed fighting that threatened to plunge the region back into chaos, four months after a fragile peace agreement was signed.
"Reports reaching here from the African forces' command in Darfur spoke of battles that have been going on since August 28 in Kukul, Sayah, Abusakeri and Gabr al-Kafud areas in North Darfur," the AU mission's spokesman Nureddin Mezni said.
Sudanese President Omar al-Beshir has consistently rejected a UN deployment in Darfur, accusing Western governments of seeking to invade his country and plunder its resources.