Khartoum - Sudan and South Sudan are talking peace after months of intermittent clashes but observers say there is still no end in sight to a rebellion in the north's border states.
Regardless of whether deals reached over the past week - including a demilitarised border zone - finally end conflict between Khartoum and the South's government in Juba, observers say Sudan will continue to face an insurgency in South Kordofan and Blue Nile.
Sudan says the South has been backing the rebels, who were not part of last week's discussions in Addis Ababa.
"Even if Juba stops its support it doesn't mean an ultimate end to this conflict," said Magdi El Gizouli, a fellow at the Rift Valley Institute.
"There are domestic local causes of this war and these causes have to be addressed."
Khartoum pushed for months to get guarantees that South Sudan would no longer back rebels of the Sudan People's Liberation Movement-North (SPLM-N), a demand which held up billions of dollars in oil revenues for both crisis-hit economies because South Sudan denies backing the insurgency.
But at last weekend's African Union-led talks, Sudan softened its stance on the security guarantees, helped an oil deal and eight other agreements including the border buffer zone to go ahead, observers say.
The two sides finally settled on detailed timetables to implement the pacts, which had remained dormant after their signing in September.
South Sudan halted crude production early last year, cutting off most of its revenue after accusing Khartoum of theft in a dispute over export fees.
Ostensibly between Sudan and South Sudan, the buffer zone on the undemarcated and disputed frontier really targets the rebels who have been fighting for almost two years, a diplomatic source said.
"It seems to me that they hope to weaken the rebels further by these agreements," said the source, declining to be named.
Lack of structure
But observers expressed concern that there was no structure for talks with SPLM-N, despite encouraging signs for Sudan-South Sudan ties after the last Addis meeting.
That is "the only weakness in this whole thing", said an African diplomat.
He said key UN officials visited Khartoum this week "to lobby for direct negotiation... at least starting with a humanitarian ceasefire" that would allow aid into insurgent-held areas.
The United Nations and the African Union have for months called on the SPLM-N and Khartoum to reach a negotiated settlement to a war which has forced more than 200 000 people to become refugees in South Sudan and Ethiopia.
An estimated one million more have been affected inside Blue Nile and South Kordofan.
The SPLM-N says it is fighting to remove the Arab-dominated regime to ensure greater democracy, respect for ethnic diversity and human rights.
South Sudan armed and trained SPLM-N when it was part of the south's rebel force but says it cut military ties before the South's independence in July 2011.
Analysts and diplomats say there is no doubt South Sudan continued to back the rebels.
If the buffer zone is established the SPLM-N "will be in a much more weakened position without a credible supply line", Gizouli said.
Juba accuses Khartoum of backing insurgents on southern territory too.
The armies of the two countries say they have begun pulling troops back 10km to implement the buffer zone which is to be supervised by dozens of monitors.
Putting that zone into effect will be a major challenge, observers say.
"So much depends on this stuff starting to be implemented, and whether they've actually withdrawn support or not," a foreign analyst said.
SPLM-N has reiterated its readiness for direct negotiations with Khartoum but the government says rebels must end hostility and cut ties with South Sudan's military first.
The rebels remain a "potential spoiler" of the Sudan-South Sudan deals and their response is uncertain, the diplomatic source said.
After the September agreements, rebels began weeks of deadly mortar bomb attacks on the South Kordofan state capital Kadugli.
"I'm afraid we will have to see more months of war in southern Kordofan," the source said.