As the fighting which is believed to have killed thousands moves towards a third week, Juba claimed that Machar, the de facto leader of rebels fighting the government, has recruited up to 25,000 young men from his Nuer tribe in the eastern state of Jonglei who it says are “ready to attack any time”.
According to Jonglei’s acting governor Ogato Chan, the Nuer fighters were around 110 kilometres (70 miles) from the state capital of Bor, which he said was calm, for the moment at least.
“The information is that they want to come and attack Bor but I am sure they will not attempt to do it because the SPLA (Sudanese army) forces will repel them back,” Chan said. “Now the army are taking position.”
Rebel spokesman Moses Ruai Lat said Machar was “not mobilising his tribe”, the second biggest ethnic group in South Sudan, describing the men instead as regular soldiers who had rejected the government and were not specifically drafted by Machar.
The accusations have cast a shadow over peace talks spearheaded by regional leaders to end the bloody violence which the international community fears could slide into civil war.
Regional leaders at the Inter-Governmental Authority on Development (IGAD) have set Tuesday as a deadline for face-to-face talks between President Salva Kiir and his former deputy to end the fierce battles for control over several strategic oil-producing areas notably in the north of South Sudan.
While the government has said it was willing to observe a ceasefire, Machar has made demands including the release of his arrested political allies before committing to a truce.
South Sudanese government spokesman Michael Makuei told AFP Sunday: “I really doubt if we, the South Sudanese government, will be in a position to sit with Riek Machar… He has not even respected the call by IGAD and the African Union to agree to the cessation of hostilities.”
Fuelled by an old rivalry between the two, the conflict has fanned ethnic differences between Kiir’s Dinka group and Machar’s Nuer clan in the country, which won independence from Sudan in 2011.
Fighting broke out on December 15 after Kiir accused Machar of mounting a coup, which his rival has denied. Rebels swiftly took over several key regional cities including Bentiu, in the northern oil-producing state of Unity, and Bor, which has since been recaptured by the army.
South Sudan’s army said calm had returned to a number of flashpoint areas in Unity state and the northeastern Upper Nile state, where troops pushed back rebel attacks.
In recent days, grim reports of massacres, rapes and killings nationwide have emerged, with the United Nations reporting the discovery of a mass grave.
Washington, which championed South Sudan’s drive for independence, as well as the United Nations and Beijing have all pressed for dialogue, with UN chief Ban Ki-moon reiterating Saturday a warning that all perpetrators would be brought to justice.
“All violence, attacks and human rights abuses must end immediately,” Ban’s spokesman said in a statement issued in New York.
“The secretary general reminds those responsible that they will be held accountable. He calls on the government and all concerned to ensure the rights and security of civilians are protected.”
More than 120,000 people are estimated to have been displaced by the clashes, according to the United Nations, which is to double its peacekeeping force to more than 12,000 to contain the carnage.
The UN refugee agency UNHCR is also investigating reports that hundreds of South Sudanese have fled to neighbouring Sudan.
South Sudan, the world’s youngest nation, became independent after a civil war that killed more than two million people between 1983 and 2005.