The Intergovernmental Authority on Development, a regional bloc of six African countries, warned it will take unspecified action to stop a conflict the United Nations says has killed more than 1,000 and forced 121,000 from their homes.
A communique from the organization issued in Nairobi indicated it would support South Sudan President Salva Kiir, saying it would not accept an overthrow of the democratically elected president.
A 2-hour closed-door meeting in Juba, South Sudan, Thursday among Kiir, Kenyan President Uhuru Kenyatta and Ethiopian Prime Minister Hailemariam Desalegn, as well as South Sudan Cabinet members and other officials, "was very constructive and very candid," but produced little progress, Ethiopian Foreign Minister Tedros Adhanom told reporters.
"The issues that we discussed were, among others, the cessation of hostilities, an immediate start of dialogue to settle the issue politically, the detainees who were suspects of the coup, and the fourth is the humanitarian crisis," he said.
But Adhanom, whose country is among those leading efforts to open peace talks between Kiir and his political rivals, announced none of the breakthroughs for which the leaders had hoped.
"We were able to agree on what needs to be done next -- it is just a question of when," an official told Britain's Guardian newspaper.
Not represented at the meeting was fugitive former South Sudanese Vice President Riek Machar, whose renegade soldiers are accused by Kiir of attempting a coup Dec. 15.
Kiir's government arrested many Machar political allies after the alleged coup attempt, which Machar says was a misunderstanding among presidential guards as fighting quickly spread across the country, escalating long-simmering tensions between Dinka and Nuer ethnic groups.
Kiir is a Dinka, the country's largest ethnic group, while Machar is a Nuer, its second largest.
Machar alleges Kiir is using the coup allegations to get rid of his political opponents.
Machar, who remains in hiding after fleeing Juba, was widely expected to be invited to send a representative to an emergency summit on the crisis in Kenya Friday.
The summit in Nairobi, to advance peace talks among Kiir, Machar and their rival supporters, is expected to include leaders of the regional eight-nation Intergovernmental Authority on Development bloc.
IGAD -- which includes South Sudan, Sudan, Kenya, Uganda, Somalia, Ethiopia, Eritrea and Djibouti -- issued a statement with the 54 nation African Union, which represents all of Africa except Morocco, expressing alarm at the spiraling, brutal violence, including reports of mass killings.
"The AU and IGAD are profoundly concerned by reports of the mobilization of tribal militias in South Sudan, which threaten to further escalate the conflict and transform it into an exceptionally destructive inter-ethnic violence that would put in danger the very existence of South Sudan," the joint statement said.
African, European and U.S. diplomats called for talks before the violence escalates into an all-out civil war.
Machar said he is ready to talk with Kiir, and Thursday called for negotiations to take place in Addis Ababa, Ethiopia, the Sudan Tribune reported, saying it spoke with Machar by phone.
But a precondition for talks is release of his jailed supporters, Machar said.
His list of delegates to the proposed talks includes senior allies imprisoned by the government, the Tribune said.
Kiir rejected Machar's preconditions.
"We are ready for dialogue with Machar, but we will not release anybody accused of a coup. They are criminals who must be brought to justice," the government said.
Delegations from China and the United Nations, which this week agreed to nearly double the number of peacekeeping forces to some 15,000, are also expected in Juba within days, the Guardian said.