The world's newest nation has struggled with chronic instability since independence in 2011, with Kiir and Machar locked in an uneasy coalition following the end of a five-year civil war.

Saturday's announcement by Martin Elia Lomuro, the minister of cabinet affairs, which said the pair had agreed on a power-sharing deal to enable the creation of a unified army, had held out hope of a potential breakthrough for its lumbering peace process.

But in a statement released late Sunday, Machar's office said no such agreement was reached.

"We strongly refute this false information and also underscore that the issue remains unresolved," the statement said.

Lomuro had earlier said the two sides would split control of senior positions in the national security command which includes the military and police, with Kiir's party holding a 60 percent share and the remainder divided between Machar and a handful of opposition parties.

Machar's party on Sunday said instead that their talks had focused on a 50:50 breakup, with the East African bloc IGAD proposing a 55:45 division "which the parties has not yet discussed".

The country's peace process has suffered from years of drift and bickering over the creation of a unified armed forces command, a key component of the 2018 truce agreement and a potential safeguard against future conflict.

The 2018 ceasefire and power-sharing deal ended a conflict that has cost almost 400,000 lives, but distrust lingered, with many of Machar's top cadres complaining they had lost out under the arrangement with the ruling party.

Earlier this month foes in Machar's party said they had ousted him as leader -- a move his allies dismissed as a "failed coup", but which raised fears for the already shaky peace process.

Machar said the squabbles were aimed at derailing the formation of a unified armed forces command.

As discontent has deepened, some citizens have called for a peaceful public uprising to topple the current regime, with a nationwide protest planned on Monday.