President Salva Kiir and rebel leader Riek Machar have agreed to a fresh ceasefire at talks mediated by the regional group IGAD. Under the deal, the warring sides have six weeks to form a unity government.
East African leaders from the regional bloc IGAD warned South Sudan's warring sides on Monday that there could be no further delays in forming a unity government and threatened sanctions if the latest agreements were not adhered to. The United States and Europe have already imposed sanctions on commanders from both sides, but diplomats say real pressure for a deal needs to come from neighboring states.
A communiqué signed by both sides in the Ethiopian capital Addis Ababa calls for the formation of a transitional government in the next six weeks that would include the new post of prime minister.
"As a region, we have to show that any party which violates agreements that there are consequences to misbehavior," Ethiopian Prime Minister Hailemariam Desalegn said at the summit.
Under the agreement, President Salva Kiir is to keep his post, while rebels loyal to his former deputy Riek Machar would nominate the prime minister, whose powers would be defined in peace talks.
Both factions also committed themselves to a fresh ceasefire, after two previous peace deals were swiftly broken, with each side accusing the other of violations.
Kiir and Machar last met in June, when they agreed to form a unity government within 60 days, but the deadline was missed.
Meanwhile, The United Nations has said the food crisis in South Sudan was the "worst in the world." Around 50,000 children face death from malnutrition, the UN said, while half the country's population need urgent food aid.