"You, collectively, by your personal and political interests are responsible for the nightmare your own people are going through," Ethiopia's foreign minister Workneh Gebeyehu told South Sudanese delegates gathered at the opening of talks hosted by the IGAD regional bloc.

"You have had numerous opportunities to change directions. You have repeatedly failed to do so. This really is the very last chance for you to accept your responsibilities and take the necessary actions to ensure South Sudanese peace and prosperity," Workneh said.

Afterwards the delegates applauded.

South Sudan won independence from Sudan in 2011, but a little over two years later its leaders began a fresh civil war pitting President Salva Kiir against his former deputy Riek Machar.

The conflict has continued killing tens of thousands, uprooting nearly four million people, roughly a third of the population, and triggering sporadic outbreaks of famine.

Various peace deals have been signed and then broken, most recently in December. Every time, each side accuses the other of responsibility for the breakdown and unrelenting violence.

South Sudan's allies have increasingly signalled their weariness with the endless warfare.

Last week the United States imposed an arms embargo on the country, and the African Union (AU) Chairperson Moussa Faki Mahamat said last month that "the time has come" to slap sanctions on those prolonging the conflict.

A 2015 peace deal that suppressed the conflict for nearly a year before collapsing had planned for elections in August this year, but the so-called troika of Britain, Norway and the US which plays an influential role in South Sudan has rejected that timetable.

"Elections in 2018 are no longer viable and cannot be supported by the troika and the rest of the international community," said Chris Trott, Britain's special representative to South Sudan.

Without peace, Trott warned that "it will become extremely difficult for us to help you rebuild your country and support your institutions."