UNITED NATIONS, Aug. 6 (Xinhua) -- United Nations Secretary-General Antonio Guterres on Monday welcomed the signing of the Agreement of Outstanding Issues on Governance and Responsibility Sharing by the South Sudanese warring parties in Khartoum, Sudan, on Sunday.

The secretary-general said it was "an important step" in the revitalization of the Agreement on the Resolution of the Conflict in South Sudan (ARCSS), which was signed on Aug. 17, 2015, in Addis Ababa, Ethiopia.

The UN chief commended the leadership of the Inter-Governmental Authority on Development (IGAD)-led High Level Revitalization Forum (HLRF) and the efforts of the Republic of Sudan to broker an inclusive political settlement of the conflict in South Sudan, the secretary-general's deputy spokesman Farhan Haq said in a statement.

"Recalling earlier agreements signed between the parties, the secretary-general urges all parties to work in good faith and demonstrate their commitment to fully implement and to finalize the revitalized ARCSS as soon as possible," said Haq.

"He reaffirms the continued commitment of the United Nations to support, in close coordination with IGAD and the African Union, the achievement of a fair, inclusive and sustainable peace agreement for the people of South Sudan," Haq added.

South Sudan's nearly five-year conflict has killed tens of thousands of people and displaced millions in the world's youngest country.

President Salva Kiir and his rival Riek Machar were in neighboring Sudan on Sunday to sign the deal, under which the rebel leader is set to return to a unity government as the first of five vice presidents.

The deal, which paves the way to a final peace accord, was signed in the presence of Sudanese President Omar al-Bashir and his counterparts from Kenya, Uganda and Djibouti, along with foreign dignitaries.

Sunday's deal was the 12th ceasefire and second power-sharing agreement between the South Sudan warring parties.