The UN's call for a pullout from the disputed frontier by Wednesday is in line with agreements for a monitored demilitarised zone made by Sudan and South Sudan around the time of the South's separation last year. The Wednesday deadline loomed as the South alleged violation of a ceasefire in effect since May 4 along the border.
Both states, Sudan and South Sudan, have failed to implement those agreements, under which they were supposed to pull back 10 kilometres (6.2 miles) from the north-south border that was in place on January 1, 1956, when Sudan became independent.
Under a May 2 UN Security Council resolution which seeks to address "a serious threat to international peace and security", both sides are to establish a "Safe Demilitarised Border Zone" and jointly begin monitoring the frontier.
The demilitarised zone would be monitored by observers from both sides, with security and other support provided by the UN's Interim Security Force for Abyei, or UNISFA, which is based in the contested region of Abyei. But a foreign diplomat has said the two sides "refused to let UNISFA deploy along the border".
The May 2 UN resolution says the call for a demilitarised zone and border monitoring "in no way prejudices" negotiations over disputed areas, and border demarcation. But Sudan's foreign ministry said it already notified the UN and the African Union that it has reservations about the demand for a demilitarised zone.
"First the two states have to agree where the border is and sign an agreement. Then after that we can do the 10-kilometre withdrawal," said the ministry's spokesman Al-Obeid Meruh.