A team of rebel officials landed in South Sudan's capital Juba on Monday to prepare for the return of the rebel leader next month and the formation of a transitional government that was agreed in a peace agreement.

President Salva Kiir and his rival, Riek Machar, the deputy president he sacked in 2013 in a political row that blew up into a conflict, signed an accord in August. But both sides have since accused the other of violating the pact with new attacks.

READ: South Sudan unity in horizon as parties agree on joint govt

Fighting has killed thousands of people, driven more than 2 million people from their homes and created a food crisis for many of the nation's 11 million people. Oil output, the main source of income, has plummeted along with global crude prices.

"Our arrival today in Juba is the end of this war, and the public should expect the arrival of my chairman and commander in chief Dr Riek Machar to Juba during January," said Taban Deng Gai, chief negotiator of the rebel group, known as SPLA-IO.

He was speaking shortly after arriving in Juba, alongside dozens of other rebel officials. About 600 rebel officials are expected to return by the end of the year.

Earlier, rebel spokesman James Gatdet Dak said the transitional government, or national unity government, would be formed by January 22.

"We hope that with the arrival of the advance team from our side such activities will successfully take off and lead to the timely formation of the transitional government," he said.

This would depend on how fast other steps agreed in the peace deal were implemented, he said.

The peace deal also included withdrawing military forces from Juba and integrating the police force and army, he said.

The government and rebel factions had been holding on-off peace talks since shortly after the conflict began in mid-December 2013, but several ceasefires agreed in the past two years were violated, often swiftly after any signing.