KHARTOUM South Sudan's ruling party on Sunday said a full-blown civil war could erupt if talks failed to defuse tensions along the border that will divide the two halves of Sudan when it separates this week.
South Sudan is due to declare independence on July 9 after southerners voted to secede in a referendum promised in a 2005 peace deal that ended decades of civil war with the north.
Preparations for the split have been marred by clashes between the northern army and armed groups linked to the south operating in the north's main oil state of Southern Kordofan, which neighbors south Sudan.
Leading members of the south's ruling Sudan People's Liberation Movement (SPLM) told reporters on Sunday there was now a risk fighting could spread into two other northern regions bordering the south -- Blue Nile and Darfur.
Southern Kordofan and Blue Nile were key battlegrounds in the last civil war and include large groups who sided with the south, many of whom fear they will be targeted after the south goes.
Darfur is the scene of a separate insurgency against Khartoum.
South Sudan's President Salva Kiir, President Omar Hassan al-Bashir, who from Saturday will only rule over the northern part of Sudan, flew to the Ethiopian capital Addis Ababa on Sunday for talks over a series of unresolved issues ahead of the split, including border violence.
Both sides last week reached a "framework agreement," effectively calling a ceasefire in Southern Kordofan. But that deal was thrown into doubt when Bashir on Friday said northern forces would continue their campaign in the state and branded a senior SPLM official there a "criminal."
"If those parties which oppose this (framework) agreement insist on aborting it, then it will create a war stretching from Blue Nile up to Darfur," the head of the SPLM's northern branch Yasir Arman said in Khartoum.
"The situation in Blue Nile is very tense. If the (northern) army disarms our forces then we have a situation like in South Kordofan ... This will be a coordinated war, definitely ... If there is a war, all sides will be looking for allies," said Malik Agar, the SPLM governor of Blue Nile.
Both Arman and Agar later flew to Addis Ababa to join the talks brokered by the African Union.
The SPLM said fighting erupted in Southern Kordofan after the north tried to disarm local fighters. The northern army says it is trying to stop an attempted uprising.
Political tensions have mounted a week ahead of the secession of the south. Both sides still have to agree on a series of issues ahead of the split including managing oil revenues and demarcating disputed parts of the north-south border.
Sudan has long been plagued by insurgencies in the country's east, west and south, led by groups angered by what they see as the political and economic domination of a small northern elite.
The northern part of the SPLM is due to become an opposition party in the north after the secession.
(Editing by Andrew Heavens and Jon Boyle)