Barack Obama on Sunday lauded the referendum held in Southern Sudan on its independence as "an inspiration to the world", dpa reported.
The peaceful polling process and the high turnout were "a tribute to the determination of the people and leaders of south Sudan to forge a better future," the president said in a statement.
Independent observers had "been extremely encouraged by the credibility of the process to date," he continued.
Polls closed on Saturday in a referendum that is widely expected to see the Christian and Animist south vote in favour of splitting from the mainly Muslim north.
Preliminary results are expected to be released by February 2, according to the Southern Sudan Referendum Commission.