(adds background By Skye Wheeler JUBA, Sudan, May 24 (Reuters) - Sudan's central government has promised that demarcation of a north-south border will be complete in time for a census vital to a referendum on possible southern secession, a southern official said on Thursday. Southerners are due to vote on possible secession of their oil-rich region in a referendum, due by 2011, that formed part of a 2005 peace deal to end more than two decades of north-south civil war. A national census, key to the success of the referendum, is now planned for November after a June 30 start date was deemed unworkable. "We have been assured that the committee will be finished before the census," said Samson Kwaje, spokesman for the semi-autonomous southern government. Kwaje said a border committee formed in 2005 to agree on the frontier, and thus pinpoint on which side of the line lucrative oil fields lie, had only started working two months ago due to a shortage of funds from the central government. Contentious areas include the oil-rich Abyei region. He said the border may not be finalised by July 9, the date after which the northern army is supposed to be north of any newly-declared frontier. But he said high level talks between the national and southern governments had given the south confidence that northern troops were preparing to move out. Under the 2005 peace accord, the south receives 50 percent of all oil revenue generated in its area. Complicated by issues of oil, ethnicity and ideology, Sudan's north-south civil war killed 2 million people and drove some 4 million from their homes.
