UN Secretary-General Ban Ki-moon called for a new unity government to be immediately set up in South Sudan after rebel leader Riek Machar returned to Juba on Tuesday and was sworn in as vice president.
Machar's return on a UN plane marked an important step in the international effort to force the rebel and government sides to implement a peace accord that was signed in August but has yet to take hold.
Ban said the rebel leader's arrival in Juba opened up "a new phase in the implementation of the peace agreement" and called "for the immediate formation of the transitional government of national unity," said a statement from his spokesman.
Under the agreement aimed at ending South Sudan's brutal war, Machar will serve alongside President Salva Kiir in a new 30-month transitional government leading to elections.
UN peacekeeping chief Herve Ladsous told a Security Council meeting that Machar's return "should open a new chapter" and "allow the real transition to begin."
South Sudan Deputy UN Ambassador Joseph Moum Malok said the new transitional government should be formed "in a day or two after consultations with the different parties in the country."
"It's vital that the parties take this opportunity to show their genuine determination to move forward with the peace process," said Ladsous.
- Turning up the heat -
US Ambassador Samantha Power said that while Machar's return marked an important step, international powers remained "clear-eyed" about the challenges ahead.
The new government will have to tackle security sector reform to end fighting, corruption and in particular, pick up the pace on plans to set up a special African Union court to try war crimes suspects, said Power.
The Security Council is determined to keep the pressure on Machar and Kiir to implement the peace accord, she added.
"When things are going to happen in South Sudan, it tends not to happen because of gravity. It happens because the international community unites and turns up the heat," she said.
South Sudan's war began in December 2013, when Kiir accused Machar of plotting a coup.
The conflict has torn open ethnic divisions and been characterized by horrific rights abuses, including gang rapes, the wholesale burning of villages and cannibalism.
Tens of thousands of people have been killed and more than two million have been driven from their homes in the violence that erupted just two years after South Sudan won independence.
Machar had been expected in the capital on April 18 from his base in the east of the country, but last-minute disputes over the security arrangements, including the weapons that rebel troops would be allowed to carry, led to delays.
