The United States is awaiting official results of Sudan's referendum on whether to split the country into two, Secretary of State Hillary Clinton said on Monday.

The completion of a peaceful, orderly Southern Sudan referendum marks a significant achievement for the Sudanese people and a historic step toward full implementation of the 2005 Comprehensive Peace Agreement, Clinton said.

The parties have an opportunity to forge a lasting and durable peace between the North and South, and to build positive relationships with the international community, she said.

We hope they will seize this moment, she added.

The seven-day poll ended on Saturday with 83 percent of registered voters casting their ballots as the task of counting them began, the Sudan Referendum Commission said on Sunday. The number of total registrants was 3.9 million.

Results are expected to be declared on February 7 or 14, the commission said.

If split, the Northern state would consist mostly of Sunni Muslims while the Southern state would contain mostly animists and Christians.