The southern region holds much of the nation's oil,
A United Nations panel will monitor the 17-day voter registration drive in 3,000 sites across the country and in eight countries abroad, CNN reported Monday.
"We know that organizing voter registration has not been easy, given the country's size and the scale of the process, but we remain confident that it can be completed successfully," said Benjamin Mkapa, chairman of the U.N. panel and a former president of Tanzania.
The January election is part of a 2005 peace agreement ending a 20-year conflict between north and south Sudan that led to the deaths of 2 million people.
The results could be a key factor in determining if Sudan is removed from a list of state sponsors of terrorism, CNN said.
The Obama administration told Sudan the United States would remove the country from the terrorist list next year if President Omar al-Bashir's government recognizes results from the secession referendum in January.
The U.N. estimates 300,000 people have been killed in conflicts in Darfur, in western Sudan, since 2003, and that 2.5 million people have fled their homes. Sudan said the death toll is not that high.