The latest round of peace talks between South Sudan's two rival leaders has failed to strike a deal on the vital issue of internal boundaries, mediators said on Friday.
Critics have accused President Salva Kiir of reorganising state boundaries to shore up his power and the issue has hobbled talks with rebel leader Riek Machar.
South Africa's Deputy President David Mabuza, mediating the talks in South Sudan's capital Juba, said the two men had agreed to a week-long arbitration process to help resolve the dispute.
The longtime rivals, whose fallout sparked a civil war in 2013, signed a peace agreement in 2018 but have missed two deadlines to form a power-sharing government.
They have held several rounds of discussions since November, when they were given 100 more days to form a unity government.
Mabuza said the talks had concluded without an agreement over states and boundaries.
"The number of states and their boundaries has been a sticking point between parties towards the formation of a transitional government of national unity," the South African presidency said in a statement Friday.
"Given that this matter has not been settled, the parties have agreed on a seven day period for further consultation on the proposal of arbitration as a mechanism to break the impasse."