Fresh talks to resolve the crisis in South Sudan have opened in Ethiopia's capital, Addis Ababa, more than two weeks after a ceasefire was signed.
Rebels agreed to continue the dialogue despite the government's refusal to release four high-profile detainees.
Both sides have accused each other of violating the ceasefire to end the conflict in the world's newest nation.
Thousands of people have died and more than 868,000 have fled their homes since it began on 15 December.
The UN says about 723,000 people have been displaced inside South Sudan and another 145,000 have fled to nearby countries, with Ethiopia receiving the largest increase in recent arrivals.
It started as a political dispute between President Salva Kiir and his former deputy Riek Machar, but escalated into full-scale conflict, with some of the fighting along ethnic lines.
The president accused Mr Machar of launching a coup - an allegation he strongly denies.
Regional mediators say the focus of the peace talks will be on political dialogue and national reconciliation in South Sudan, which gained its independence in July 2011.
BBC South Sudan analyst James Copnall says finding some sort of political settlement between the warring parties will not be easy and a political deal alone will not be enough to resolve the country's problems
He says it will take a broader process, involving a wider spectrum of society, addressing community healing across South Sudan, which is one of the world's least developed nations.
'Hiding in the bush'
Rebel negotiators agreed to continue with talks after they say they received assurances that their demands would be addressed - these include the release of detainees and the withdrawal of Ugandan troops aligned to Mr Kiir.
Eleven prominent political figures from a faction of the governing SPLM party, who are allies of Mr Machar, were taken into custody when Mr Kiir first made the allegations of an attempted coup.
Seven of the detainees have been released into Kenyan custody and may attend the talks, but four remain in jail in South Sudan's capital, Juba.
Meanwhile, the medical charity Medecins Sans Frontieres says thousands of people are facing life threatening conditions in the bush near the town of Leer in Unity state.
MSF staff members fled Leer hospital on 30 January just before the town came under attack, taking the most critically ill patients with them.
"The staff who remain in touch with MSF report that worsening security has pushed them further into the bush," Raphael Gorgeu, MSF's head of mission in South Sudan said in a statement.
"They have split into smaller groups to decrease the chance of attack and divided their supplies of medicines, which they are saving to treat only the most life-threatening cases."