Leaders from northern and southern Sudan are holding negotiations on how to run the country after next year's referendum that will determine if the south becomes an independent state.

Tuesday's talks are focusing on a range of unresolved issues between the two sides -- including demarcating the border, citizenship and the sharing of oil revenues and Nile water resources.

The semi-autonomous south is scheduled to hold a referendum January 9 on whether to become an independent state.  The vote was a key part of the 2005 agreement ending Sudan's north-south civil war.

Much of Sudan's oil wealth is believed to lie along the disputed border. The oil-rich Abyei region holds a separate referendum January 9 on whether to be part of the north or the south.

Some information for this report was provided by AP, AFP and Reuters.