By Aaron Maasho
ADDIS ABABA, Feb 13 (Reuters) - Officials freed from jail in South Sudan who have joined peace talks have demanded the government release four more political prisoners, warning failure to do so will undermine the negotiations.
The talks in Addis Ababa secured a ceasefire last month in a conflict that has claimed the lives of thousands of people and displaced more than half a million in South Sudan, the world's youngest country, since it erupted on December 15.
They were due to start on Monday but have been delayed until seven former prisoners accused of plotting a coup, including former ministers of justice and finance, arrived in Ethiopia.
The rebel side demands that four remaining political detainees - out of 11 originally detained by the Juba government - be released and the Ugandan army, which has backed President Salva Kiir, withdraw from South Sudan.
The seven, freed on Jan. 29, arrived on Wednesday night but talks are yet to start.
South Sudanese politician Deng Alor Kuol, a former cabinet minister and one of those released, said the success of the talks may hinge on whether Juba releases the four prisoners.
"It is difficult. If you want meaningful and successful talks they better release the four detainees," Kuol said.
The East African bloc IGAD, which is mediating the talks, the United States and other backers have all called on President Kiir's government to release the four detainees.
Taban Deng Gai, head of rebel leader Riek Machar's delegation at the negotiations, said the launch of the latest round was now in doubt.
"What will the talks produce if Uganda is messing up the country? They (the South Sudan government) are also still keeping behind bars people who can contribute at the talks," he told Reuters, in reference to the four prisoners.
"The mediators should convince us why this phase of the talks is important while we didn't even implement the little that we have now. All is in doubt."
The rebel delegation on Monday said it would boycott the talks but changed its mind when IGAD mediators assured them their grievances would be addressed in the discussions.
Machar was vice president of South Sudan until Kiir sacked him last year. The political dispute quickly led to violence between ethnic groups.
The two delegations will travel to the resort town of Debre Zeit some 40 km (25 miles) south of Addis Ababa on Friday, with the mediators hoping to bring both sides together for direct talks.
Each side has accused the other of massacres and ethnically-based reprisals. (Editing by Drazen Jorgic and Andrew Roche)