Talks continue between Sudan and South Sudan as they try to resolve simmering disputes over oil, borders, and citizenship issues.

A VOA correspondent at the scene, in Ethiopia's capital Addis Ababa, says the talks are focusing on border issues, while the African Union mediation team seeks common ground on the more contentious issues of citizenship and oil revenues.

South Sudan has accused Sudan of charging excessive fees for the use of oil pipelines that run north to the Red Sea. A source close to the talks told VOA the south is offering to pay about $0.69 a barrel, while Khartoum is demanding a package worth $36 a barrel.

The source says southern negotiators are also demanding any agreement include reference to the enslavement of southerners, which they say continues even after independence.

The two sides met late Wednesday to discuss whether it was worth continuing the dialogue, which was scheduled to last 10 days, but devolved into a shouting match on Tuesday.

Earlier Wednesday, South Sudan said it is considering building a temporary pipeline along the Nile river to the capital, Juba. The oil would then be transported on trucks to ports in Kenya and Djibouti.

This dispute over fees has prompted South Sudan to shut down all oil production, a move analysts say is likely to financially hurt both countries.

The south took over most Sudanese oil production when it became independent last July, but relies on pipelines through the north to get the oil to market.

The sides also disagree on borders of the oil-producing Abyei region, and accuse each other of supporting the other's rebel groups.

On Tuesday, the U.N. Security Council expressed “grave concern” about cross-border violence between the two Sudans. The world body said it has reports of troop movements and airstrikes along the poorly-defined border, and demanded that all parties cease military operations in the area.

The council also urged the countries to respect a non-aggression pact they signed less than a month ago.