Juba - Peace efforts in South Sudan were in tatters as warring rivals blamed each other for attacks and the army claimed that the rebels had broken their own peace deal hours after signing.The government of the world's youngest nation has refused to ink the power-sharing deal, despite the threat of sanctions and mounting international frustration at the failure to seal a peace accord.It prompted the African Union to warn on Wednesday that the rivals would bring "disaster" on themselves and the region if no deal is signed.The 20-month-long war shows no sign of stopping."There was a heavy attack by the rebels, but we fought back in self-defence and repulsed them," army spokesman Philip Aguer told AFP, describing battles on Wednesday in the Manyo district of the north-eastern oil-producing Upper Nile state.The blame gameRebels accused the government of wanting a military solution, and said they were attacked near the small but strategic southern town of Pageri on Tuesday, on the main road south from the capital Juba towards the Ugandan border.Rebel general James Koang Chuol said his troops had then seized Pageri, claiming they now controlled the key highway.Aguer, however, said the government was in control of Pageri.He dismissed the rebel claims as "lies", saying that while two government soldiers were killed in fighting, they were attacked by unknown gunmen raiding cattle.Reports of fighting could not be independently confirmed, but the blame game came after a Monday deadline ended to sign a peace deal.While rebel chief Riek Machar signed the document at talks in Ethiopia, President Salva Kiir only initialled part of it, and said he would return to the table in early September to finalise the accord.The US state department said Kiir had told Secretary of State John Kerry that he has "every intention" of signing the agreement."He said he needed a couple more days of consultations but he made it very clear that it was his intention to sign," a spokesperson said.Aguer, meanwhile, accused the rebels of breaking the deal. "You cannot sign a peace agreement and then launch an attack hours later," he said.'Failure of leadership'The UN aid chief for South Sudan Eugene Owusu, in a ceremony on Wednesday remembering the 29 aid workers murdered in the war as well as the "many more" missing, said that "indifference amongst those in power leaves too many without hope".Nearly 70% of the country's population is facing food shortages while nearly 200 000 terrified civilians are sheltering in UN bases."Fighting in South Sudan has caused immense suffering and loss for millions," Owusu said.Meanwhile, international anger at the standoff is growing with the United States and Britain on Tuesday pushing for UN sanctions against the government.US National Security Advisor Susan Rice accused Kiir's government of a "failure of leadership" and said it had "squandered" another opportunity to end a conflict that has killed tens of thousands and plunged the country into chaos.Security and stability African Union Commission chief Nkosazana Dlamini-Zuma also condemned the setback. "Deadlock in the peace process can only spell further disaster for South Sudan and its people, with far-reaching implications for regional security and stability," she said in a statement.The government, which has called the proposed deal a "sellout", says it is not possible to sign a credible peace accord because the rebel forces have split.Powerful rebel general Peter Gadet and other key commanders earlier this month accused Machar of seeking power for himself, and said they would fight both their former comrade and the government.South Sudan has been torn by fighting between forces loyal to Kiir and rebels allied with Machar, his former deputy, since December 2013 and the violence has exploded along ethnic lines."The conflict must end," Owusu said. "We cannot and must not turn our backs on the people of South Sudan."