Ethiopia's Prime Minister Hailemariam Desalegn called for international action at the "highest level" to end South Sudan's civil war after a deadline for a peace agreement passed yesterday in his capital Addis Ababa.

Desalegn's Friday statment, addressed to the South Sudanese people, may signal a shift in approach by the Intergovernmental Authority on Development (IGAD), the regional bloc led by the prime minister which is mediating the peace talks.

The United Nations and the African Union look to IGAD for guidance on using sanctions or other targeted measures to end the war.

But Desalegn said IGAD has not produced results of peace so will refer to the wider international community to take stronger action.

"Our efforts cannot continue unaltered and expect a different outcome." he said. "The peace process must be reinvigorated and reformed. In the coming days, I will consult with my colleagues, the IGAD leaders, partners and friends in the region, on the continent, and beyond to agree a common plan of action."

"At the the highest level, the world must speak with one voice on South Sudan...We will use all influence at our disposal to convince those that remain intransigent," he said, without specifically mentioning sanctions or other targeted measures against war leaders.

War leaders abdicated "sacred duty"

Desalegn further said that Kiir and Machar have abdicated their responsibilities as leaders by continuing the war.

"Leadership is never easy, but continuing a war flagrantly disregards the interests of you, the people. It is an abdication of the most sacred duty leaders have to you, their people: to deliver peace, prosperity and stability," he said.

"Both President Kiir and Dr. Riek Machar have assured the Leaders of the IGAD Member States that they are committed to peace. At the same time, there are individuals on both sides who continue to beat the drums of war," he said.

"This cannot be right."

File photo: IGAD Chairman and Ethiopian Prime Minister Hailemariam Desalegn (left) with IGAD Special Envoy and former Ethiopian Foreign Minister Seyoum Mesfin, February 2014