The head of a United Nations panel monitoring the upcoming referenda on whether southern Sudan secedes from Africa's largest country has expressed concern over the lack of progress in several key areas, especially voter registration, with less than three months remaining until people head to the polls.

The three-member body -- appointed by Secretary-General Ban Ki-moon and led by former Tanzanian president Benjamin Mkapa -- wrapped up its week-long visit to Sudan on Friday.

"We have been pleased to hear from all the parties that they are committed to playing their part to make the referenda a success," Mr. Mkapa said at a press conference in Khartoum.

On 9 January, the inhabitants of southern Sudan will vote on whether to secede from the rest of the country, while the residents of the central area of Abyei will vote on whether to be part of the north or the south.

The referenda will be the final phase in the implementation of the Comprehensive Peace Agreement (CPA), which was signed in 2005 to end two decades of warfare between the northern-based Government and the Sudan People's Liberation Movement/Army (SPLM/A) in the south.

Mr. Mkapa, who witnessed the pact's signature in Nairobi, Kenya, said that the two referenda represent its "decisive milestone."

He voiced hope that "the wonderful relief and optimism of that day can be reflected here, whatever the outcome of the votes."

But he expressed the panel's deep concern about the oil-rich Abyei area, "which is crucial for peace and stability in Sudan," said the panel's leader. "The situation on the ground there is reported to be very tense."

He said that the body is aware of continued efforts by the parties to find an "acceptable solution."

Another round of talks is slated to take place later this month, and it is "vital that they succeed so that the Abyei referendum can take place," the panel leader said.

He also pointed to the "negatively charged atmosphere" on both sides, with threats and accusations being made. "Toning down the rhetoric will go a long way towards easing tensions and promoting dialogue and it will contribute to providing a conducive environment for the referenda."