South Sudan now faces the worst food security crisis in the world. Violence has forced over 1.5 million people from their homes since mid-December, while more than 50,000 children under the age of five are at risk of dying from malnutrition this year. This is not a crisis caused by drought or flood: it is a calamity created by conflict. Unless the fighting ends and a peace agreement is concluded, the number of those at risk of starvation -- now as many as 3.9 million people, fully one-third of the population – will reach even more catastrophic levels.

South Sudan's leaders need to make choices and they need to make them now if they're going to pull their country back from the brink of famine. In the last months, I've traveled to Juba and Ethiopia to press on the cease-fire. I've had call after call with both leaders in South Sudan, pressing them to work closely with regional partners in support of mediation efforts. The United States has spoken out against ongoing fighting, obstruction of humanitarian access and failures to resolve the conflict.

But in the end, the leaders have to make decisions. President Salva Kiir and former Vice President Riek Machar share responsibility for triggering this man-made crisis and they share responsibility for ending it. I call on them to end the fighting immediately and negotiate in good faith under the auspices of the Intergovernmental Authority on Development.

The Government of South Sudan and the opposition must put the safety and wellbeing of the South Sudanese people first by immediately implementing the Cessation of Hostilities Agreement, ensuring the security of humanitarian workers and goods, and dismantling unofficial checkpoints that impede the delivery of aid. International and South Sudanese humanitarian workers have saved lives at great personal risk. They must be able to do their jobs without the threat of violence, informal “taxation” or other arbitrary impediments.

The United States remains committed to the people of South Sudan and has provided more than $456 million in humanitarian aid this year alone. We call on fellow donor countries to make additional contributions. The people of South Sudan deserve the opportunity to begin rebuilding their country, and to develop the national and local institutions they need to put South Sudan on a path towards stability.