United Nations Secretary-general Ban Ki-moon has welcomed an agreement on security and cooperation issues reached by Sudan and South Sudan.

Presidents Omar al-Bashir of Sudan and Salva Kiir of South Sudan signed the agreement at a ceremony in Addis Ababa Thursday, after four days of talks.

Mr. Ban commended the two leaders for choosing peace instead of war, but he expressed regret they could not agree on a disputed oil-rich region. He urged the two countries to continue their efforts to resolve the issue of the contested territory. He also expressed concern about the continuing humanitarian crisis in Sudan's South Kardofan and Blue Nile states, which have been affected by north-south violence.

The agreement call for a demilitarized zone along the two countries' border and the resumption of southern oil exports through the north. Another deal calls for creation of a so-called “soft border” that will allow people, goods and animals to move across “unhindered.”

The two Sudans remain divided over who controls the oil-producing Abyei region and other border areas.

Despite that, South Sudan's President Kiir hailed Thursday's agreement as a major breakthrough.

“…as we witness the signing of the cooperation agreement that brings to an end the long conflict between our countries on post-secession issues.”

The north and south fought a 21-year civil war that led to the South's independence in July 2011.

Lingering issues pushed the countries to the brink of war earlier this year. Sudan has accused the South of arming rebels in two of its states, while South Sudan accuses the north of launching air attacks.

South Sudan cut off oil exports through northern pipelines in January over a disagreement on transit fees. The lack of oil revenues has hurt the fragile economies of both nations.

The United Nations has threatened both countries with sanctions if they do not settle their issues.

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