US President Barack Obama urged Sudanese leaders on Monday to ensure a peaceful referendum on the partition of Africa's largest country as he hailed voter registration as a "critical milestone."
"The president is extremely pleased that voter registration has begun in Southern Sudan in preparation for the January 9th, 2011 referendum on self-determination," a White House statement said.
"Voter registration is a critical milestone in that process, and we hope that it will continue unabated."
South Sudan president Salva Kiir appealed to southerners to sign up en masse as registration kicked off on Monday after a three-month delay.
"We call on northern and southern leaders to finish the work started with the voter registration process to ensure the referendum is peaceful and occurs on time, and that the will of the people of South Sudan is respected regardless of the outcome," the White House statement said.
"Both parties also must urgently work to find an agreed-upon way forward for Abyei in the interest of lasting peace, and we call on the government of Sudan to fully fund the Southern Sudan referendum commission."
Registration offices will remain open until December 1 for the vote, which is to be held on the same day as a referendum in the oil-rich Abyei region, with voters there choosing to stay with the north or go with the south.
The referendum, part of the 2005 deal that also created a power-sharing government with Kiir as vice president to Sudanese President Omar al-Bashir, is viewed as a gateway to freedom in the south.
Tension still hangs over the process, although the African Union said the north and south have agreed to settle key issues such as border demarcation and trade barriers.