The arrival of South Sudan’s deputy rebel chief to the capital signals that the civil war “has come to an end”, a senior official welcoming him has said.
Alfred Ladu Gore said he was happy to be back in Juba after more than two years of fighting – and the rebels wanted to “proclaim peace”.
He is leading an advance party ahead of rebel leader Riek Machar’s return.
Mr Machar, now at his HQ in the eastern town of Pagak, is to arrive on Monday to take up the post of vice-president.
The deadly civil conflict erupted in December 2013 after President Salva Kiir accused Mr Machar, who was once his deputy, of plotting a coup.
Mr Machar denied the charges, but then mobilised a rebel force to fight the government.
Since then thousands of people have died and more than two million fled their homes.
Last week, more than 1,300 rebel troops were flown to Juba as part of the terms of the peace deal signed in August 2015.
These forces are deployed to provide security for Mr Machar, who said he would not come to take up his new position until these security measures were put into place.
A senior member of the ruling SPLM party said the arrival of Mr Gore in Juba was a significant moment for the country and showed the commitment by both sides to implement the peace deal.
“His arrival today signifies that indeed the war has come to an end. And that the suffering inflicted on the people of South Sudan face by this unwanted war will be brought to an end and that peace shall reign once again in this country,” Akol Paul said.
Peace agreements between both sides have broken down repeatedly over the years, so there is still expected to be mistrust within this new government, the BBC’s Africa security correspondent Tomi Oladipo reports.
But the people of South Sudan have seen enough calamity and can only hope this transitional government gets things right this time, our correspondent adds.
The peace agreement was signed amid a threat of sanctions from the United Nations.
Fighting was supposed to stop immediately – but there have been frequent violations.
President Kiir and Mr Machar have agreed to share out ministerial positions. The agreement returns the government to where it was before the war broke out.
The UN and African Union have accused both sides of carrying out atrocities – an AU-backed report in January alleged that 50 civilians had suffocated after government troops locked them in a shipping container.
South Sudan is the world’s youngest country and one of the least developed. It split from Sudan in 2011.