Both sides in the conflict in South Sudan have agreed to meet for peace talks in Ethiopia to try to halt the violence that has killed at least 1000 people.
The conflict erupted more than two weeks ago between supporters of President Salva Kiir and those of his sacked deputy Riek Machar. More than 121,600 people are believed to have fled their homes.
The United Nations says there is mounting evidence of atrocities and mediators warn that continued fighting could scupper the talks in Addis Ababa on Wednesday.
Forces loyal to rebel leader Mr Machar are reported to be back in control of the strategic town of Bor, the capital of the vast Jonglei state and site of an ethnic massacre in 1991.
The BBC reports the first priority should be agreeing on terms of a cessation of hostilities. Next would come the potentially challenging issue of resolving the political fractures that created the crisis.
President Kiir has already told the broadcaster that he will not contemplate sharing power with Mr Machar.
Mr Machar, who was sacked in July last year, denies there was a plot to overthrow Mr Kiir.
The fighting initially broke out in South Sudan's capital, Juba, and has now spread to many parts of the country.
Western and regional powers have pushed both sides to end fighting that has cut South Sudan's oil output and raised fears of a full-blown civil war in the heart of a fragile region.