JUBA U.N. Secretary General Ban Ki-moon urged South Sudan's warring parties on Thursday to choose peace over politics as both sides squabbled over blame for protracted delays in forming a transitional government.
Oil-producing South Sudan seceded from Sudan in 2011 and in December 2013 descended into civil war after a dispute between President Salva Kiir and his sacked deputy Riek Machar.
Both sides, under pressure from Washington, the United Nations and other powers, signed a preliminary peace deal in August and agreed to share out ministerial positions in January. But that accord has broken down repeatedly.
Ban met Kiir in Juba and said he had spoken by phone to Machar, who has refused to return to the capital unless the government demilitarises the city.
The U.S. government this week warned of sanctions against both sides if the peace process definitively collapses.
"My message to the leaders of South Sudan is clear: put peace above politics, pursue compromise, overcome obstacles. Establish the transitional government of national unity without delay," Ban told reporters in Juba.
"The parties must know that responsibility doesn't end with the signing of an agreement. In many ways, it begins. And it must begin now," Ban said.
On Wednesday, U.S. Secretary of State John Kerry said Kiir and Machar, who was reappointed to his old post this month, would face individual sanctions if they did not deliver on the deal, warning of a "critical moment for South Sudan's survival".
A spokesman for Kiir, Ateny Wek Ateny, said the threat "must be aimed at those who are putting impediments into the implementation process ... The problem is not with Salva Kiir."
He said Kiir was ready to form a transitional government "tonight" if Machar's side, the SPLM/A-IO, submitted the names of their candidates for the cabinet.
James Gatdet Dak, spokesman for the SPLM/A-IO, said Machar's side was "ready to deliver" and Kerry's comments were helpful.
"This is a good statement because it can put pressure on the two parties. But on our side we are ready to deliver, it is the government that has been violating the peace agreement."
(Writing by George Obulutsa and Drazen Jorgic; Editing by Edith Honan and Mark Heinrich)