Secretary-General Ban Ki-moon proposed a new U.N. mission for South Sudan after it becomes independent on July 9, requesting 7,000 troops to protect civilians and a mandate to help the new government prevent conflict and consolidate peace.

Ban's proposal in a report to the Security Council was circulated Tuesday, as the U.N.'s most powerful body was visiting Sudan.

But it was written before serious fighting erupted last week in the disputed oil-rich Abyei region on the border between the Arab-dominated north and mainly ethnic African south. The clashes threaten to unravel a 2005 peace deal that ended more than two decades of civil war and re-ignite the fighting.

The south voted overwhelmingly to secede from Sudan, Africa's largest country, in a January referendum called for under the peace agreement. But key provisions of the 2005 agreement have not been resolved.

The secretary-general called the dispute over the future status of Abyei "the greatest challenge" to implementing the peace accord.

He urged leaders from both sides to demonstrate "political will" and solve key issues including setting the north-south borders, resolving Abyei's future through the referendum called for in the peace agreement, and agreeing on security arrangements.

Ban said the best way is through the framework established in the 2005 agreement until an alternative arrangement is found. That framework includes the only forum for the parties to meet, under U.N. auspices, to prevent or mitigate conflict on either side of the border, including Abyei.

"I therefore cannot stress enough the critical nature of these negotiations and the responsibility that rests on the leaders of the two states to reach agreements that will provide the foundation for peace and security in the Sudan and South Sudan and the region as a whole," the secretary-general said.

The government of South Sudan has asked for the U.N. to establish a follow-up mission after the current mandate expires on July 9, but the government in Khartoum has not.

Ban urged the north and the south, and the Security Council, to consider extending the mandate of the current 10,400-strong U.N. peacekeeping mission for three months, from July 9 to Oct. 9.

During that period, Ban said, the U.N. will start reducing its presence in the Sudanese capital, Khartoum, and focus on assisting both sides to maintain calm and resolve outstanding issues including finding an acceptable arrangement for monitoring the border.

The secretary-general said he will report to the Security Council in September on progress toward settling these issues.

In the meantime, he said, he plans to establish an advance team to set up the new U.N. mission to support the independent state of South Sudan "as it undertakes its peace consolidation and peacebuilding efforts."

Ban said the mission's main thrust should be political, to assist the government "in preventing conflict, consolidating the peace, strengthening the pluralistic political system, and addressing issues related to peace, governance and reconciliation." It should also support the government in pursuing a new constitution and holding elections, if requested, he said.

While most of the mission's mandate would be under Chapter 6 of the U.N. Charter, which outlines peaceful ways to settle disputes, Ban's said his proposal "to protect civilians under imminent threat of physical danger" should be under Chapter 7 of the Charter which is militarily enforceable.

He proposed a 7,000-strong military force, taking into account the need for deployment over a wide area, including some places "at high risk of conflict." He also called for 900 international police to "assist the government in establishing solid foundations for an efficient, community-oriented police service following democratic principles and capable of providing security and protection."