Major foes in the years-long conflict in South Sudan have embarked on a new round of peace talks to end the deadly war in the country.

The talks between President Salva Kiir and arch-foe Riek Machar in the Sudanese capital Khartoum began on Monday, with Sudanese President Omar al-Bashir and Ugandan President Yoweri Museveni mediating the negotiations that many hope would end South Sudan’s four-and-a-half-year brutal civil war.

The talks come after a first meeting in Ethiopia on Thursday failed to achieve any breakthrough. Regional East African leaders have been struggling to come up with a solution to the conflict in South Sudan, the world’s newest country which would be hit with United Nations sanctions if it fails to put an end to the bloodshed.

Tens of thousands of people have been killed and nearly four million others displaced as a result of the war, which erupted in December 2013 when disputes intensified between Kiir and his then deputy Machar. The two met face-to-face for the first time in two years in Addis Ababa on Wednesday, but failed to reach any agreement. South Sudan’s government said right after the meeting that it “had enough” of Machar.