Peace talks aimed at ending 15 months of civil war in South Sudan appeared deadlocked on Thursday just hours before the expiry of a regionally-imposed deadline for a deal.
Hopes of an agreement were dealt another blow as President Salva Kiir and rebel leader Riek Machar pulled out of their discussions, promising to reconvene mid-afternoon.
"We are working very hard to meet the deadline, but there are still a number of remaining issues," a diplomat involved in the negotiations told AFP.
"There's still a lot of hard work to do."
A deadline set by the east African regional bloc IGAD, which is mediating the talks and growing increasingly frustrated with the lack of results, expires at midnight (2100 GMT).
The latest round of negotiations to solve the deadly conflict in the world's youngest nation has gone badly from the start.
Kiir and Machar shunned the opening of talks on February 23, only met directly for the first time on Tuesday and broke off talks on Thursday.
"The two principles will meet again this afternoon after separate meetings with the mediators," said an IGAD spokesman.
IGAD chief mediator Seyoum Mesfin called this -- the eighth round of talks -- the "last chance" for ending the conflict and diplomats insist there will be no extension of the deadline.
"Doing that would undermine the current talks," said one diplomat. "We are focusing on reaching an agreement today."
A failure to reach a deal could see a wider push for sanctions -- with diplomats' patience running out and the peace process having already cost well over 20 million euros ($22 million) with no nothing to show for it.
South Sudan's war began in December 2013 when Kiir accused Machar, his former deputy, of planning a coup.
Fighting quickly turned ethnic with Dinka soldiers loyal to Kiir accused of massacring members of Machar's Nuer tribe in the capital Juba.
The violence spread and has been characterised by tit-for-tat ethnic murder, rape, pillage and the widespread use of child soldiers.
Tens of thousands have been killed and two million uprooted by fighting.
Peace talks were convened by IGAD within weeks of the outbreak of civil war but have only achieved a string of failed ceasefires and broken promises.
In a bid to force a deal, the United Nations this week passed a resolution that will allow the imposing of sanctions on individuals deemed to be undermining peace efforts -- including leaders or officials who obstruct peace talks, impede humanitarian aid deliveries, recruit child soldiers or attack UN peacekeepers.
The US ambassador to the United Nations, Samantha Power, told the council that the resolution -- which also raises the possibility of an arms embargo -- would give African mediators leverage in their push for agreement by making clear that "those who frustrate peace must begin to pay the price".