A leading figure in the Sudan Peoples Liberation Movement has said Sudan may ask the United Nations to organise the referendum in the border region of Abyei. The region is less than seven months from deciding whether to be part of North or South Sudan.

But Yasir Arman said on Sunday that leaders had failed to agree on who should join a commission to organise the referendum.

He said that unless key issues were resolved soon, UN involvement would be the only way to come to an agreement. The former opposition SPLM joined President Omar al-Beshir's government after elections earlier this year.

Abyei is perhaps the most important bit of land in Sudan because the oil under it produces about half of all Sudan's oil production.

Oil profits make up about 98 per cent of the government of Southern Sudan's budget and about 60 per cent of the national government's budget in Khartoum. So neither side is keen to lose this important region, and they're running out of time with just six months to go.

The comprehensive peace agreement signed in 2005 between the north and the south includes an independence referendum for the whole of southern Sudan. And the South is intent on making sure that it's not delayed.

The April elections, the first democratic elections in 24 years, were delayed by a year. In another contested oil-rich area, Southern Kordofan, a "popular consultation" process is far behind schedule but is going through a census this month.

So the South is pushing forward on Abyei in the hopes that there's no reason to delay the independence referendum in January.