By Peter Martell (AFP) – 23 hours ago

JUBA, Sudan — Former enemies from north and south Sudan committed themselves on Tuesday to work for "sustainable peace" during negotiations for a referendum on potential independence for the south.

Top leaders signed a document of "guiding principles" for the negotiations, to ensure they are "informed by a shared belief in a prosperous future of all Sudanese people, rather than burdened by a difficult past."

The National Congress Party (NCP) of Sudanese President Omar al-Beshir and the former rebel Sudan Peoples? Liberation Movement (SPLM) which rules in the south, are negotiating on key outstanding issues for the referendum.

These include wealth sharing of oil and other resources as well as questions of nationality and citizenship, should the south choose independence.

"The parties recommit themselves to the holding of the referendum on self-determination for the people of Southern Sudan on the 9 January 2011, and to respect the choice of the people," the document read, signed in the southern capital Juba.

South Sudan is still recovering from a 22-year civil war with the north during which about two million people were killed, in a conflict fuelled by religion, ethnicity, ideology and resources like oil.

The referendum was set up under a 2005 peace deal, which promised the south the chance to choose independence or to remain within a united Sudan.

Several analysts have warned of the risk of war if the negotiations stumble, with concern growing that sticking points can be resolved in time.

However, Pagan Amum, who signed the document on behalf of the SPLM, said it would ensure negotiations worked towards creating a "permanent peace, and establish good relations between the south and the north."

One of the NCP representatives, Mutif Siddiq, said the deal would "make the outcome of the referendum -- regardless of the vote -- a peaceful one."

The document was witnessed by former South African president Thabo Mbeki, who is mediating the discussions as part of an African Union panel.

"This essentially marks the beginning of post-referendum negotiations, " said Mbeki, following the signing.

"It indicates the commitment by all the negotiators to attend to all of these matters with necessary seriousness and the urgency that is required."

Talks will resume on July 27, with separate groups focusing on four specific areas including economic and resource management, citizenship, security and international treaties, Mbeki said.