A peace deal aimed at ending 20 months of civil war in South Sudan was given a cautious welcome Thursday, but rebels condemned government reservations that undermine fundamental parts of the accord.
Facing the threat of international sanctions, President Salva Kiir signed the agreement on Wednesday at a ceremony in Juba, but he annexed a list of reservations that he said would have to be addressed for the deal to take hold in the world's newest nation.
The deal gives the rebels the post of first vice president, which means that rebel chief Riek Machar would likely return to the job from which he was sacked in July 2013, an event which put the country on the path to war later that year.
But the 12-page government document calls this a "humiliation" and a "reward for rebellion", and insists the post of first vice-president must be on equal footing with the current vice-president, whose post remains.
It also criticises plans to demilitarise the capital, and objects to the powers of the foreign-led Monitoring and Evaluation Commission -- the body that will police the implementation of the deal -- that will report to the international community.
Machar in turn said the reservations "casts doubts" on the government's commitment.
"All of us have reservations, but we didn't taint our signature with reservations, because it would mean we are reopening the negotiations," Machar told AFP in Ethiopia.
Machar, who signed the deal on August 17, insisted he was "committed to implement it".
The UN Security Council has given Kiir until September 1 to get fully behind the agreement or face possible sanctions, and the United States has circulated a draft resolution that would impose an arms embargo and targeted sanctions on those who undermine peace efforts.
The United States, the key supporter of South Sudan's split from Khartoum in 2011, welcomed the signing and said the peace deal should be implemented as it stands.
"We do not recognise any reservations or addendums to that agreement," US National Security Advisor Susan Rice said in a statement from Washington.
Fighting erupted in December 2013 when Kiir accused Machar of planning a coup, unleashing a wave of killings that has split the country along ethnic lines. At least seven ceasefires have already been agreed and then shattered within days or even hours.
Under the latest deal, a permanent ceasefire must come into force by nightfall on Saturday.
African Union Commission chief Nkosazana Dlamini-Zuma said the deal was "a critical step in the efforts aimed at ending the conflict" but said the agreement must be implemented.
Key aid agencies, which are struggling to stem a humanitarian crisis in the devastated nation, said in a joint statement that even if implemented, the deal was "only the beginning of a long, hard journey towards peace and reconciliation."
Tens of thousands of people are thought to have died in a war marked by ethnic killings, gang rapes and child soldier recruitment.
"The value of the peace deal will only be seen on how it is implemented on the ground," the International Rescue Committee said.
"The people of South Sudan need more than words," said John Hoare from CARE aid agency. "They need real commitment from their leaders to ensure that this is a lasting peace, that the violence has ended and the reconciliation process can begin."
The deal was brokered by the regional eight-nation IGAD bloc, along with the UN, the African Union, China, Britain, Norway and the United States.
Some 2.2 million people have been driven from their homes in the conflict. About 200,000 terrified civilians are sheltering at UN bases.