International pressure is critical to end fighting in conflict-torn South Sudan and get the feuding political leaders to agree on a transitional unity government by the August 10 deadline, the top UN envoy says.
Hilde Johnson told a news conference that "the situation in South Sudan is bleak" and time is short.
Fighting broke out in the world's newest nation in December after President Salva Kiir, an ethnic Dinka, accused former vice-president Riek Machar, an ethnic Nuer, of trying to oust him in a coup. That sparked months of ethnic attacks. Cease-fires in January and May didn't hold.
Johnson said "fighting has gone down" since the latest ceasefire on June 10, but it must stop completely and a new government must be formed.
The toll has been huge, with thousands killed and more than 1.3 million people forced to flee their homes, including nearly 100,000 who sought refuge in UN peacekeeping camps.
Johnson said progress at the negotiating table is even more urgent because of the threat of famine in a few months, which "might hit levels and proportions that beat what we have seen before in South Sudanese history, and maybe in the region". The fighting has left farmers unable to plant crops.
Johnson will be stepping down as the UN special representative on July 8 after what she called three crisis-filled years that began with the country's independence from neighbouring Sudan.
She said she had seen tensions in South Sudan's leadership but didn't expect "the speed, the scale, and the scope" of the violence that erupted in December.
The rifts in the country "are deeper than they've ever been and ... there needs to be a very deep, thorough, healing and reconciliation process from the bottom up" which will take "a very long time", Johnson said.
But she warned that this won't work without accountability and justice "for the atrocities" and grave human rights violations that have been committed.
Nonetheless, Johnson said, she isn't leaving on a totally despondent note.
"From my experience in South Sudan, one thing I've learned is anything can happen, and they have an incredible capability of putting things behind them and reconciling," she said. "They have an incredible capability of shaking hands with their former enemies. It has happened throughout South Sudanese history, and that's why at this point in time I'm also hopeful that it will happen again."