South Sudanese rebel leader Riek Machar returned to the capital Tuesday and took the oath as the country's top vice president.
Machar's arrival raises hopes the government and rebels can move ahead with a peace deal signed last year to end the country's 30-month civil war.
After the swearing-in, President Salva Kiir said he and Machar "will immediately proceed to form the Transitional Government of National Unity" called for in the peace accord.
He said this is the "only choice" to return South Sudan to the path of unity and prosperity.
Machar, in his comments, promised to cooperate with President Kiir.
Machar was Kiir's vice president once before. It was his firing in July 2013 that set off the war in December of that year. Since then, fighting has killed tens of thousands of South Sudanese and displaced more than 2 million from their homes.
Machar's plane landed at Juba International Airport on Tuesday, after more than a week of delays as the government and rebels argued over the size and weaponry of the rebel force deployed to protect him in the capital.
In New York, South Sudanese Ambassador Joseph Malok said that despite the delays, South Sudan's government remains committed to fully implementing the peace deal. He said the new transitional government would be formed "in a day or two, after consultations with the different parties in the country."
The United Nations had pressured both the government and rebels to ensure that Machar returned. Monday, a U.N. spokesman said, "We'd like to see him back as soon as possible; it's an integral part of hopefully returning some peace to South Sudan."
On Monday, one of Machar’s top officials arrived in Juba from Gambela, Ethiopia, along with nearly 200 military personnel.
Like Machar, General Simon Gatwech was expected to arrive last week, but officials said his chartered plane was not granted permission to land by South Sudan's government until Sunday evening.
Dressed in a green military uniform, Getwech disembarked at Juba International Airport along with 195 SPLM-in-Opposition military officers, 20 rocket-propelled grenades and 20 machine guns, per an agreement reached between government and SPLM-IO officials.