Sudan's President Omar Hassan al-Bashir has ruled out any chances of a deal over three disputed regions at the ongoing peace talks in Kenya.
The two sides have agreed to share oil wealth
He said the talks with southern rebels had no authority to settle the status of Abyei, Nuba mountains and Blue Nile.
Correspondents say Mr Bashir's stand may scuttle the peace process.
Control of the regions is one of the outstanding issues at the talks aimed at ending 20 years of war, after the two sides agreed to share oil wealth.
The United States has been trying to broker a deal and its special envoy John Danforth has joined rebel leader John Garang and Sudanese Vice President Ali Osman Taha at the talks.
"We have no mandate to resolve this issue in the current
talks in Naivasha, one issue in the peace talks on
southern Sudan remains, that is participation in power," Mr Bashir said.
The BBC's Alfred Taban in Khartoum, says the Sudanese People's Liberation Army (SPLA) has been lobbying for Abyei region to be placed under its control.
Many SPLA top ranking officials come from the area which is also believed to have some oil deposits.
The disputed regions are mainly arid areas whose boundaries were changed during the colonial period.
Last week the Sudanese Government and southern rebels finalised an agreement on how to share the country's wealth.
Under the overall agreement, the oil revenue is to be shared equally on a 50-50 basis.
The conflict in Sudan between the Christian and animist South and mainly Muslim North has devastated the country and left an estimated 4m people displaced and 2m dead.