"We are going back to Uganda until we are informed by the chief mediator when the Lord's Resistance Army will be ready to sign," Internal Affairs Minister Ruhakana Rugunda said on the remote Sudan-Congo border.

Rugunda said a separate signing ceremony by Ugandan President Yoweri Museveni that was planned for April 15 in the south Sudanese capital Juba had been indefinitely postponed.

"Unless circumstances significantly change, the government of Uganda has no plans to extend the cessation of hostilities agreement," he said. That truce expires on April 15.

The draft deal between Kony's LRA and the government had appeared to be nearing failure overnight after the elusive guerrilla leader asked mediators to clarify parts of the text.

Sources involved in the talks said he later fired his chief negotiator.

Uganda's 22-year civil-war has killed tens of thousands of people, uprooted 2 million more and destabilised neighbouring parts of oil-rich south Sudan and mineral-rich eastern Congo.

Kony and two of his top deputies are wanted for war crimes by the International Criminal Court in The Hague, including rape, murder and the abduction of thousands of children to serve as fighters, porters and sex slaves.