The statement did not say whether there was another round of talks planned, but noted that mediators "remain hopeful that the promise of peace will be fulfilled in the near future."
Ethiopian Prime Minister Hailemariam Desalegn said in a statement Friday that he regretted "the talks did not produce the necessary breakthrough," adding that the failure was disappointing for mediators and observers who had tried their best to urge the warring factions to make concessions for peace.
"The consequences of inaction are the continued suffering of you, the people of South Sudan, and the prolonging of a senseless war in your country," the statement said. "This is unacceptable, both morally and politically."
The statement did not say whether there was another round of talks planned, but noted that mediators "remain hopeful that the promise of peace will be fulfilled in the near future."
The spokesman for the U.N. secretary-general said Ban Ki-moon expressed profound disappointment over the failure of Kiir and Machar to "display statesmanship" and reach a deal. Ban had spoken with both parties in the past two days to urge them along.
The threat of U.N. sanctions hangs over Kiir and Machar, as the U.N. Security Council this week unanimously approved the creation of a system to impose sanctions on those blocking peace in their country.
The conflict has killed tens of thousands of people since December 2013, when the armed forces in the South Sudanese capital of Juba appeared to splinter along ethnic lines. Since then, there has been sporadic violence as government forces loyal to Kiir, an ethnic Dinka, try to put down rebel forces loyal to Machar, an ethnic Nuer who used to be Kiir's deputy before he was fired in July 2013.
The political rivalry between Kiir and Machar is widely believed to have sparked the current crisis, the reason international diplomats and observers have been calling for a political solution in the form of a unity government in South Sudan.