The United Nations is pushing regional leaders to exert pressure on Juba to end the violence that has turned tribal, pitting Kiir's Dinka community against ethnic Nuer, Shilluk and other groups.
South Sudan's government is spending oil revenue on weapons as the country descends into a famine largely caused by President Salva Kiir's military campaign, a confidential UN report says.
The report obtained by AFP on Friday calls for an arms embargo on South Sudan — a measure that has been backed by the United States but was rejected by the Security Council during a vote in December.
"Weapons continue to flow into South Sudan from diverse sources, often with the coordination of neighbouring countries," said the report by a UN panel of experts.
The experts found a "preponderance of evidence (that) shows continued procurement of weapons by the leadership in Juba" for the army, the security services, militias and other "associated forces."
South Sudan derives 97 percent of its budget revenue from forward sales of oil. From late March to late October 2016, oil revenues totalled about $243 million, according to calculations from the panel.
At least half — "and likely substantially more" — of its budget expenditures are devoted to security including arms purchases, the 48-page report said.
The government continued to sign arms deals as a famine was declared in Unity State, where 100,000 people are dying of starvation and a further one million people are near starvation.
"The bulk of evidence suggests that the famine in Unity State has resulted from protracted conflict and, in particular, the cumulative toll of repeated military operations undertaken by the government in southern Unity beginning in 2014," said the report.
The government is blocking access for humanitarian aid workers, compounding the food crisis, while significant population displacement is also contributing to the famine.
An upsurge in fighting since July has devastated food production in areas that had been stable for farmers, such as the Equatoria region, considered the country's breadbasket.