President Salva Kiir presided over a ceremony that launched the process, part of a peace deal reached with rival Riek Machar in 2018.

The world's youngest country, South Sudan has been governed by provisional constitutions during the years of civil war that followed independence in July 2011.

"This workshop is to develop a roadmap for the permanent constitution of the Republic of South Sudan," Kiir noted.

"It is absolutely critical that it reflects the aspirations of our people for freedom, equality, justice and prosperity for all," he added.

The ceremony was attended by all sides that signed the 2018 accord, along with international envoys from the African Union, European Union and United Nations.

Few provisions of the truce have been honoured however, and analysts have warned of the threat of a return to war in an oil-rich country that remains severely underdeveloped and poorly managed.

For Oyet Nathaniel, who represented the former rebel group Sudan People's Liberation Movement-in-Opposition (SPLM-IO) of Machar who is now vice president, the constitution to be finalised within two years must curb some presidential powers.

"The powers given to the president are unacceptable. We expect people to regain back their powers in the new constitution," he told AFP.

One example is the current president's power to dismiss elected officials such as governors or parliamentary deputies.

South Sudan plunged into civil war in December 2013 after Kiir accused Machar of plotting to overthrow him.

The vicious conflict, during which rape was used as a weapon of war, killed more than 380,000 people and left four million homeless.

In February 2020, a coalition government was formed and the bitter rivals agreed to end the fighting, though local conflicts continue to erupt periodically, often over cattle raiding.

More than 1,000 people were killed in violence between rival communities in the last six months of 2020.

Earlier this month, and in accordance with the peace agreement, Kiir finally dissolved and then reconstituted the national assembly to include opposition members.