NAIVASHA, Kenya - Sudan's Vice President Ali Osman Taha and southern rebel leader John Garang held talks for the third straight day here Saturday in a bid to revive the faltering peace process and end Africa's oldest ongoing civil war. Taha and Garang, leader of the rebel Sudan People's Liberation Army (SPLA), returned to the negotiating table at around 1:30pm (1030 GMT) Saturday after meeting long into the night on Friday, an AFP reporter at the scene witnessed. "Both sides have shown genuine willingness to resolve the problem in Sudan," chief mediator Lazaro Sumbeiywo, a former Kenyan army general, told AFP in Naivasha, 80 kilometres (50 miles) northwest of the Kenyan capital Nairobi. "It seems they all understand that war can not go on forever and that the peace process is irreversible," added Sumbeiywo. He said the two sides, under pressure to reach a settlement, were addressing substantive issues in the conflict and were not just trying to revive the peace talks that stalled last month. Khartoum and the SPLA struck a breakthrough accord in July 2002 which granted the south the right to self-determination after a six-year transition period and exempted the mainly Christian and animist region from Islamic laws practiced in Khartoum. Subsequent rounds of talks focused on how to share power and resources during the six-year interim period of self-rule for southern Sudan. But Khartoum has rejected a draft final document unveiled by mediators from the Intergovernmental Authority on Development (IGAD) - East Africa's regional body - charging that implementing the measures would lead to secession by the oil-rich south. Khartoum's stance on the final draft led to the peace process stalling on Aug. 23. One of the mediators, Eritrean ambassador to Kenya Mohamed Omaro, on Friday described the Naivasha talks as a "do-or-die session," noting: "Delegates surely cannot go to the next round of talks with good morale if these two leaders fail to agree." Sudan, Africa's largest country, has suffered civil unrest since independence in 1956, but the current civil war started in 1983 when the SPLA took up arms to end domination of the south by Khartoum. The war has, directly and indirectly, killed more than 1.5 million people and displaced more than four million others. Meanwhile in Khartoum, the office of the peace adviser to Sudanese President Omar Al Beshir on Saturday denied reports that he had been sidelined from the negotiations with Garang or had presented his resignation. An official in Ghazi Salaheddine Atabani's office said he was currently still serving as peace adviser, despite reports to the contrary in an official Egyptian newspaper, Al Ahram. Citing non-official Sudanese sources, Al Ahram reported that Atabani had decided to quit after being replaced at the Kenya peace talks by Taha. Atabani is not part of the delegation in Naivasha. But the official in Atabani's office said Taha "was presiding over the high peace council and there is no contradiction between his role and Mr Atabani's."