South Sudanese President Salva Kiir and his rival, rebel leader and former vice president Riek Machar, have agreed to complete talks on the creation of a transitional national unity government within 60 days.

The conflict between their respective forces started as a power struggle on December 15, 2013 and escalated into an ethnic conflict. There were fears it could descend into genocide after the United Nations said the rebels had massacred hundreds of civilians in Bentiu in April 2014.

Mediators from the 8-nation East African regional bloc known as the Intergovernmental Agency for Development (IGAD), to which South Sudan belongs, threatened the two sides with sanctions if they didn't cease all military operations in the conflict.

IGAD chairman Ethiopian Prime Minister Hailemariam Desalegn said if Kiir and Machar didn't abide by the agreement "IGAD as an organization will act to implement peace in South Sudan."

Desalegn also referred specifically to "sanctions" and other "punitive actions." It is the first time that South Sudan's neighbors have issued such a warning.

Mediators were frustrated by the failure of previous agreements, including two ceasefires.

Casie Copeland, an analyst specializing in South Sudan with the International Crisis Group (ICG), told DW the two sides are going to find it very difficult to overcome their entrenched positions.

"The government says they were legitimately elected and the rebels were trying to overthrow them and take power by force. So they don't believe they should be asked to engage in any sort of transitional arrangement."

Copeland said the rebels, too, have their reasons for being intransigent.

"They believe their people were attacked and they are fighting to defend the Nuer ethnic group from a state that was quite violent towards civilians at the beginning of the conflict. They think that if they don't continue to fight, the government can't be trusted, if they lay down their arms the government won't make any changes at all," the ICG analyst said.

The deal also binds the two sides to permitting unhindered humanitarian access to the hundreds of thousands of people who have fled their homes since the fighting began in December. Aid experts fear severe hunger could hit South Sudan because residents have not planted crops during the fighting. The United Nations has been warning that four million people could be on the brink of starvation by the end of the year.

Despite this committment to a transitional government by Kiir and Machar, there are still plenty of unknowns.

"The transitional government remains a very unclear concept. We don't know what its composition will be, we don't know what its mandate will be, we don't know the time frame - a short period to usher in elections? Is it a longer period in which we are going to fundamentally change the nature of the state and pass the new constitution which is well overdue? These are the questions which will indicate both how serious a political agreement the transitional government is going to be and also how serious the parties are," Copeland said.