The defence ministers of Sudan and South Sudan on Monday cut short talks on demilitarising the tense border and other security issues, but negotiations are going well, the South's minister said.
John Kong flew in from Juba on Sunday for talks with his Sudanese counterpart Abdelrahim Mohammed Hussein.
A conference room was prepared complete with flags of the two countries, place names for members of each delegation, and snacks in heated trays on the side.
But in the end, the two ministers stood next to each other to tell reporters the issues are being referred back to Addis Ababa, Ethiopia, where an African Union mediation panel is based.
"We are not meeting today," Kong said but described the negotiations broadly as "very successful" so far without elaborating.
"There is nothing that made this meeting to be short," he said.
The presidents of Sudan and South Sudan agreed more than two months ago to establish the demilitarised buffer zone to cut support for insurgents -- allegedly backed by the South -- and to allow a resumption of South Sudanese oil exports through northern pipelines.
The deals came after their countries fought a border war in March and April. They were part of a wide-ranging package signed in September to resolve security and economic tensions but which have not been implemented, sparking international concern.
Monday's meeting of the Joint Political and Security Mechanism was supposed to be a followup to similar talks from 6-7 November in South Sudan's capital Juba.
After the Juba meeting failed to agree on how to put into effect the September deals, the African Union stressed "the need for the full and timely implementation of the security arrangements."
"We are referring this meeting to Addis Ababa," where the mediators will gather on Saturday, Kong said.
Ahead of the Khartoum talks observers said progress on demilitarising the undemarcated border between Sudan and South Sudan would be uncertain.
An African diplomat said the focus was on trying to start joint monitoring by the two countries of the proposed demilitarised zone.
"We are expecting we will do it," Kong said when asked about the monitoring.
Khartoum has repeatedly accused South Sudan of supporting the South's former civil war allies who are fighting in Sudan's border states of South Kordofan and Blue Nile.
Sudan has insisted that security be assured before economic deals are implemented.
The South separated in July 2011 under a peace agreement that ended a 1983-2005 civil war.