South Sudan rival leaders given 100 days to form unity government

South Sudan President Salva Kiir and rebel leader Riek Machar have been given another 100 days to form a power-sharing government after failing to resolve differences over a peace deal.

The two leaders, whose fall out in 2013 sparked a conflict that has left hundreds of thousands dead, were granted the extension after a rare face-to-face meeting held with regional heavyweights in Uganda.

It is the second time the deadline has been pushed back since the rivals signed a truce last September that brought a pause to fighting.

Both sides had agreed to join forces in a coalition government by November 12.

But with the date looming and key issues far from resolved, regional leaders brokered high-level mediations in Entebbe to chart a way forward.

"It was really impossible to have them reach agreement in five days. We've given them three months and we will continue our engagement," Ugandan Foreign Minister Sam Kutesa told AFP following the closed-door discussions at State House in Entebbe.

The meeting "agreed to extend the pre-transitional period... and to review progress after fifty days from that date", Kutesa said after the meeting, reading from an official communique.

Ugandan President Yoweri Museveni, General Abdel Fattah al-Burhan, who heads neighbouring Sudan's sovereign council, and Kalonzo Musyoka, a special envoy from Kenya, were among top delegates at the regional gathering.

The peace deal has largely stopped the fighting that erupted just two years after South Sudan achieved independence, violence that left nearly 400,000 dead and displaced close to four million people.

Observers had warned pushing the foes to form a unity government before disagreements over security and state boundaries were resolved threatened to plunge the country back into war.

"Another extension is far preferable than a return to conflict," said Alan Boswell, senior analyst at the International Crisis Group (ICG) think tank.

"Regional mediators must step up at the highest levels to finally resolve the sticking points blocking the peace process from moving forward."