Direct talks between South Sudan's warring factions have been delayed amid concerns that the world's newest nation is sliding toward civil war.
Officials in Ethiopia say the face-to-face peace talks that were expected to begin Saturday in Addis Ababa have been put on hold because there is no agreement on an agenda.
Delegates for South Sudan's President Salva Kiir and ex-vice president Riek Machar gathered in the Ethiopian capital several days ago, in a bid to end fighting that has left more than 1,000 people dead and 200,000 internally displaced.
The two sides have spent most of the time holding separate talks with mediators from the East African regional bloc IGAD (Intergovernmental Authority on Development). Negotiators had hoped direct talks would start on Saturday but now say the timetable is uncertain.
Meanwhile, fighting continues in Bor, the rebel-held capital of Jonglei state. Government troops have been advancing on Bor in a bid to retake the city.
Earlier, forces loyal to Machar said they were preparing to advance from Bor to the national capital, Juba. But in a Friday interview with "The Telegraph," Machar said his forces would hold back on attacking the capital in hopes of achieving a "negotiated settlement."
South Sudan's unrest began in mid-December, when renegade soldiers attacked an army headquarters. President Kiir accused former vice president Machar of a coup attempt.
Machar told VOA Wednesday that President Kiir is responsible for much of the unrest. He said peace cannot be achieved under the president's leadership.
Witnesses say some of the violence is ethnically motivated, with supporters of Kiir, a member of the Dinka tribe, and supporters of Machar, from the Nuer tribe, targeting each other.
On Friday, the U.S. embassy in Juba ordered the evacuation of more staff due to the "deteriorating security situation."
An embassy statement urged all U.S. citizens to leave and said the embassy can no longer provide consular services to Americans in South Sudan. The U.S. has also announced plans to send additional humanitarian aid to South Sudan.
South Sudan gained its independence from Sudan in 2011, following decades of conflict.