South Sudanese President Salva Kiir and arch-foe Riek Machar were set to hold a new round of peace talks Monday after a first meeting last week faltered.
Sudanese President Omar al-Bashir is hosting in Khartoum the second round of talks between the two bitter rivals, aimed at ending South Sudan's four-and-a-half year brutal civil war.
A first round brokered by Ethiopian premier Abiy Ahmed in Addis Ababa on Thursday failed to achieve any breakthrough.
Regional East African leaders have launched new efforts to secure peace in South Sudan where warring factions face a looming deadline to avert UN sanctions.
The war has killed tens of thousands of people and driven about four million others from their homes.
It erupted after Kiir fell out with his then deputy Machar in December 2013, dashing the optimism that accompanied independence of South Sudan just two years earlier from Sudan.
"In this round of talks we are looking for a breakthrough to this thorny issue," Sudanese Foreign Minister Al-Dierdiry Ahmed told reporters on Sunday.
Kiir and Machar's meeting in Addis Ababa was their first face-to-face encounter in nearly two years.
Their meeting in Khartoum will be the first since fighting erupted in South Sudan.
It comes after South Sudan's government declared that it "had enough" of Machar, dashing hopes of any breakthrough at the Addis Ababa talks.
"As the people of South Sudan, not the president alone, but as the people of South Sudan, we are saying enough is enough," South Sudanese government spokesman Michael Makuei said Friday.
Makuei rejected Machar's presence in any transitional government but did not rule out the involvement of other rebel figures.
His remarks show the personal enmity between Kiir and Machar, that lies at the heart of the conflict, is as strong as ever.
Before the start of talks in Ethiopia, Machar's SPLM-IO rebel group had also dismissed the latest peace efforts as "unrealistic".
South Sudan descended into civil war after Kiir accused Machar of plotting a coup against him, sparking violence between the two factions that was fuelled by brooding ethnic tensions.
Since a 2015 peace deal collapsed in July 2016 with Machar fleeing to South Africa, Kiir's government has gained the upper hand militarily as the opposition has splintered into a myriad of factions.
Initially largely fought out between South Sudan's two largest ethnic groups -- Kiir's Dinka and Machar's Nuer -- smaller groups have since spawned their own militias raising question marks about the ability of either leader to halt the war.
In May, the UN Security Council gave the two warring sides a month to reach a peace deal or face sanctions.
A landlocked state with a large ethnic mix, South Sudan gained independence from Sudan in 2011 after a long and brutal war.