South Sudan has described a proposed deal with the rebels as a "sell-out" after abandoning peace talks mediated by the African Union (AU) in the Ethiopian capital of Addis Ababa.

"It is a sellout, and we will not accept it," South Sudanese Information Minister Michael Makuei told reporters on Tuesday as President Salva Kiir returned home from the Monday talks.

"We strongly believe that this [peace] document cannot save the people of South Sudan," the minister said, adding that the government in Juba would now discuss the deal with the people for 15 days.

Intense international efforts have been under way to strike a peace deal between the South Sudan government and the rebels.

The two sides appeared to be closing the deal on Monday, when President Kiir pulled out of the talks and returned to his country for more consultations, postponing the signing of the peace deal.

The South Sudanese president had warned from the start of the peace talks that it would not be possible to sign a credible peace deal amid a rift among rebel forces.

President Kiir was quoted as saying that a peace deal that "cannot be sustained cannot be signed."

Rebel leader Riek Machar, however, signed the deal, and urged President Kiir to reconsider his move. “It was an opportunity for us to end the war,” Machar said.

The international community had threatened that South Sudan could potentially become the subject of sanctions if a deal was not reached between the two sides.

Meanwhile, the chief mediator in the talks, Seyoum Mesfin, said the government has “certain reservations” and will return after consultations.

“In the next 15 days, the president will come back to Addis Ababa, Ethiopia, and finalize the peace agreement,” he said.

The conflict between the government and rebels broke out almost two years ago when Kiir accused his ex-deputy, Machar, of plotting a coup against him. Machar denied the accusation and formed a rebel army against the president.

The United Nations says the conflict has placed more than half the 12 million population in the country in need of relief aid and forced some 2.2 million people out of their homes.