Peace talks between South Sudan's government and rebels will extend beyond a Thursday deadline set by mediators to allow them to finalise details on power sharing, mediators from the regional East African group IGAD said.
The group had allowed to the end of Thursday to iron out any issues that were keeping the two sides from reaching a conclusive deal to end fighting that erupted in December 2013 after a political dispute that saw President Salva Kiir sack Riek Machar as deputy president.
"The Special Envoys urge the Principals to use the limited time that remains to make progress on the outstanding issues of the mediation agenda," IGAD said in a statement without giving details.
According to the latest roadmap issued last month talks were to be completed by March 5, with the goal of a transitional government by April.
An IGAD spokesman said the negotiations would run until Friday 0700 GMT, while diplomats participating in the talks said a power sharing structure between the rebels and the government was yet to be worked out.
"The security area, the power sharing area ... the scope of the structure and the levels, these are the critical areas that has still kept the parties apart and they are tackling them," Seyoum Mesfin, IGAD chief mediator, told reporters.
The fighting has killed more than 10,000 people and driven more than 1.5 million from their homes. The conflict has broadly followed ethnic rifts that pre-date independence.
On Tuesday, the UN Security Council established a sanctions regime for South Sudan but stopped short of imposing worldwide travel bans and asset freezes on officials in the conflict-torn country or an arms embargo.
The resolution threatens to blacklist anyone undermining security or interfering with the peace process.
South Sudan has expressed its displeasure at the resolution.
IGAD has so far been unsuccessful in its attempts to mediate an end to the civil war, which has created a humanitarian crisis. In early February, Kiir and Machar forged another ceasefire agreement aimed at pushing them closer to a final deal to end the conflict that has hurt the oil-producing state.