Updated

The United States special envoy to South Sudan is urging President Salva Kiir's government to start political reforms to resolve the country's crisis.

Donald Booth said Friday that "the fundamental questions" that sparked armed conflict in mid-December must be addressed for lasting peace to prevail in South Sudan, the world's newest country.

Booth spoke to reporters in the Ethiopian capital of Addis Ababa, where 34 African leaders attended the summit of the African Union.

South Sudan has seen violence since Dec. 15, when a fight among presidential guards in the capital escalated into a rebellion that threatened to topple the government.

Riek Machar, the ousted former vice president who now commands rebel forces, has called Kiir a dictator who should be removed from power.