More than three million southerners have signed up for the 9th January, 2011 poll, which is likely to split Africa's largest country in two, and create the continent's first new country since 1993.
Disputes and delays in registering voters had led many to suggest the vote would have to be postponed, an outcome that would likely please northern leader Omar al-Bashir, but threaten to return the country to violence.
There has been renewed international engagement in recent months, however, and the registration process proceeded smoothly in the semi-autonomous southern region. Despite the registration period, which was meant to end on 1st December, being extended for a week, it looks likely the vote will go ahead on time.
The independence referendum is the outcome of the 2005 Comprehensive Peace Agreement (CPA), which ended a 20 year civil war between the largely Arab north and largely non-Arab south, which claimed more than two million lives.
Though the peace has held since 2005, there is great mistrust between the northern National Congress Party (NCP), headed by President al-Bashir and the southern Sudan's People's Liberation Movement (SPLM). The SPLM have accused the NCP of trying to derail the referendum, and many southerners living outside the south chose not to register for the referendum, fearing that Khartoum would tamper with their votes.
A central issue is revenues from oil, as most of the country's hydrocarbon resources are located in the south. Currently the revenue from Sudan's 500,000 daily barrels of oil is shared between the north and the south, but the north stands to lose up to 75 per cent of its petrodollar income if the south separates.
Many southerners believe that al-Bashir will try to postpone the referendum to maintain its income. The UN and the international community, especially the US, have played a hands-on role in recent months, trying to induce al-Bashir to accept the results of the referendum, through offers of the easing of sanctions and debt relief. The International Crisis Group (ICG) thinktank has said in a recent report that al-Bashir's government was stalling to extract as many concessions from the south and the international community as possible.
Even if the vote does go ahead on schedule, key parts of the CPA, including demarcation of the north-south border and how oil will be managed, has not been decided. The oil issue is particularly tricky because the pipelines from the southern oilfields run through the north.
A number of southern figures backed by the NCP have recently announced that the vote is in violation of the interim constitution and the CPA, and are in the process of finalising a lawsuit against the South Sudan Referendum Commission (SSRC). The group has said they will ask for an injunction to prevent the SSRC from proceeding with its preparations for the referendum. If granted, it means that the exercise will have to be delayed until the court rules on the challenge. The lawsuit could be filed as early as Wednesday 8th December, according to the Sudan Tribune.
The NCP has in recent weeks accused the SSRC head Mohamed Ibrahim Khalil of turning a blind eye to 'blatant' violations committed by the SPLM in the registration process. They allege that the SPLM has intimidated potential voters not to register in order to make it likely that the referendum will result in a vote for succession.
Despite these issues, and the very tight deadline, it seems likely that the southern Sudanese will vote on 9th January, 2011. The same cannot be said of the Abyei region, which was due to vote to join either the north or the south on the same day. North-south talks on Abyei broke down in Ethiopia last month, and northern officials have said it would be impossible to hold on the vote on time.
US State Department spokesman Philip Crowley admitted as much on 7th December, when he said "I think we have a recognition that that referendum will not go forward on January 9th, but we continue to encourage the parties to work on a solution to Abyei."
The Abyei referendum commission has yet to be appointed and the parties remain divided on voter eligibility. There is some speculation that the vote will not take place at all in oil-rich Abyei. Rather, there may be a negotiated settlement, for example Abyei going to the south in exchange for something the north wants, according to Zach Vertin of the ICG.