Peace talks aimed at ending the South Sudan conflict have been extended indefinitely after the government and rebels missed the deadline for a deal.
The talks in Ethiopia are being mediated by the East African regional bloc, Igad, which had given both sides until Thursday to reach agreement.
The UN imposed limited sanctions this week and the US warned both sides of further steps if no deal was reached.
The 14-month conflict has displaced 1.5 million people and killed thousands.
Igad's chief mediator in the talks, Seyoum Mesfin, said the United Nations and the African Union may now play a direct role in the negotiations.
However, he did not say whether Igad would push for the UN to impose further sanctions on both parties, as he had earlier warned.
The US this week said that an arms embargo and other punitive measures are possible if the two sides cannot agree a deal.
However, the government of South Sudan has warned that the imposition of any US-backed sanctions would be counter-productive and harm the peace process.
Attempts at maintaining a ceasefire have failed because of fighting that many argue has had ethnic overtones.
South Sudanese rebels have warned that the peace talks could collapse if the government refuses to give more ground, especially over the vexed question of power sharing in a unity government.
The war began when President Kiir accused Mr Machar - his former deputy - of planning a coup.
Mr Machar denied the coup allegation, but then raised a rebel force to fight government troops.
The fighting has mainly been between President Kiir's Dinka ethnic group and the Nuer group, which Mr Machar belongs to.
Mr Kiir has led South Sudan, the world's newest state, since its independence from Sudan in 2011.