Sudan and South Sudan have asked the African Union to help hammer out details of a proposed withdrawal of troops from their disputed border, defense ministers from both countries said on Monday, as stalled talks continued to delay oil exports.

Week-long negotiations in Khartoum failed to reach an agreement on how to withdraw their armies, a step both sides had said was necessary to resume oil exports from landlocked South Sudan through Sudan.

"We will meet in Addis Ababa on the 15th to continue our meeting and dialogue on how to implement the cooperation deals signed by Sudan and South Sudan in Addis Ababa," Sudan's defense minister, Abdel Raheem Mohammed Hussein, told reporters.

His southern counterpart, John Kong Nyuon, said some "issues" remained unresolved. The talks in the Ethiopian capital will be brokered by AU mediator Thabo Mbeki.

In September, the former civil war foes agreed to end hostilities and restart oil exports after coming close to war in April, the worst violence since South Sudan seceded from Sudan last year after decades of civil war.

South Sudan's top negotiator Pagan Amum had raised hopes for the Khartoum talks by saying oil exports could restart this month. But Juba has delayed turning on oil wells, originally scheduled for November 15.

South Sudan, which inherited three-quarters of oil production when it broke away, shut down its output of 350,000 barrels a day in January after tensions over pipeline fees escalated.

Lingering disputes have continued to fuel conflict between the neighboring countries.

Sudan said last week it will not allow South Sudan's oil exports to flow through its territory until Juba cuts ties with anti-Khartoum rebels and expels their leaders, dampening hopes bilateral tensions were over.