South Sudan's president has agreed to hold direct talks to end the conflict in the country with his rival, US Secretary of State John Kerry has said.
He said the meeting between Salva Kiir and the rebel leader, Riek Machar, could take place as early as next week.
Mr Kerry, who is on a visit to the South Sudanese capital, Juba, said he would be talking to Mr Machar later by phone to get his agreement.
More than a million people have fled their homes since December.
Fighting broke out after President Kiir accused his sacked deputy Mr Machar of plotting a coup.
Mr Machar denied the charges, but then mobilised a rebel force to fight the government.
Their power struggle has taken on an ethnic dimension as politicians' political bases are often ethnic.
The BBC's Emmanuel Igunza in Juba says a face-to-face meeting - even as a mere gesture - would be a game changer in the conflict.
The two sides negotiated a truce in January and have resumed talks in Ethiopia, but the violence has continued.
On Thursday, Mr Kerry warned that if the fighting continues to target civilians along ethnic lines it "could really present a very serious challenge to the international community with respect to the question of genocide".
After his meeting with Mr Kiir, the US diplomat said that "before the promise of South Sudan's future is soaked in more blood" both sides had to find a way to end the crisis.
"I told President Kiir that the choices that both he and the opposition face are stark and clear. And that the unspeakable human costs that we have seen over the course of the last months and which could even grow if they fail to sit down are unacceptable to the global community," he said.
Mr Kerry said that he had already arranged for the direct talks between the men - who fought together in the civil war before South Sudan's independence - to be mediated by Ethiopia's Prime Minister Hailemariam Desalegn.
President Kiir was open to taking steps to halt the hostilities and "engage with respect to a transitional government", he added.
The UN has about 8,500 peacekeepers in South Sudan, which became the world's newest state in 2011 after seceding from Sudan.
Mr Kerry has said that he hopes another 2,500 soldiers - which are likely to come from Ethiopia, Kenya and Rwanda - will be deployed within the next few weeks with a stronger mandate from the UN Security Council.
The US secretary of state's peace efforts will be followed on Saturday by a regional heads of state mini-summit to be held in Juba.
Mr Kerry is on a four-nation tour of Africa, which began in Ethiopia and ends on 5 May.