North and South Sudan have made "significant" progress on a wide range of follow-up arrangements between the two States following the southern region's vote for independence, the top United Nations envoy in the country said Wednesday.

"Much of the ground work has already been completed. Both parties are engaging seriously and making progress," Secretary-General Ban Ki-moon's Special Representative Haile Menkerios told the Security Council, citing agreement in principle on open borders, good neighborly relations, non-interference in each other's affairs, a framework for non-aggression and military cooperation, citizenship, residency and property ownership.

The two sides are also working towards mutually beneficial arrangements on oil revenue sharing and other economic matters, he said.

Menkerios was briefing the Council following the 7 February announcement of the official results of the South's referendum showing that an overwhelming majority opted for secession from what until now has been Africa's largest country.

The vote was the culminating point of the 2005 Comprehensive Peace Agreement (CPA) ending two decades of civil war between the North and the South that killed some 2 million people and drove an estimated 4.5 million others from their homes, and Mr. Menkerios noted that "against the odds" the Sudanese Government not only contributed to holding the referendum but accepted its outcome.

"Indeed, 7 February will have to be remembered and celebrated in Sudan's and Africa's history as a day when the longest running civil war in the continent's recent history came to a definitive end, when the spirit of peace and cooperation prevailed over the spirit of war," he said, voicing the hope that "the goodwill generated by the referendum will translate into increased momentum and finalization soon" of all post-referendum arrangements.

He noted that both sides have committed to resolve by the end of March the status of Abyei, an area straddling northern and southern Sudan, that was due to have voted in a separate but simultaneous referendum on which side it would join. But a referendum commission has yet to be established there, and there is still no agreement on who would be eligible to vote.

Throughout the referendum period, the nearly 10,500-strong UN Mission in Sudan (UNMIS) intensified its peacekeeping patrols in Abyei after reports of clashes between Arab Misseriya nomadic cattle-herders linked to the North and the Dinka ethnic group linked to the South.

Menkerios noted that Abyei police have committed to withdraw its units from the field into the town, allowing the seasonal Misseriya migration to start, while the Misseriya have agreed to remove roadblocks currently preventing traffic from entering Abyei from the north.

"Serious challenges remain, however," he warned. "Despite tireless efforts by UNMIS to support improved inter-tribal relations, tensions in the area continue. Given the delicacy of the current environment, I urge all parties to redouble their efforts to keep the peace on the ground, while taking advantage of the political momentum they have built in other areas to conclusively address the deeper issues driving the conflict in Abyei."

As for the future of UNMIS, Menkerios said the South has indicated it would welcome UN engagement to consolidate peace and capacity building of the new State's institutions, while discussions are continuing with the North on areas where they may seek future cooperation with the UN.

"This is a new, historic moment for Sudan, a new dawn that, if built upon, can lead to sustainable peace and progress in Sudan and contribute to the same in the immediate region and throughout the continent," he concluded.

In a presidential statement, the Council called on the international community to lend its full support to help all Sudanese people build a peaceful and prosperous future, saying it looked forward to welcoming an independent South Sudan as the UN's 193rd member after its expected formal declaration of independence on 9 July.