"The two principals will meet in Addis Ababa upon the invitation extended by his excellency, Prime Minister Abiy Ahmed," Meles Alem, a spokesman for Ethiopia's foreign ministry, told AFP.

South Sudan's ambassador to Ethiopia, James Pitia Morgan, confirmed Kiir's planned attendance, as did Manasseh Zindo, a senior official in Machar's SPLM-IO rebel group.

The two leaders, whose political rivalry triggered the start of a civil war more than four years ago have not met since Machar and his forces were chased from the capital during fighting in July 2016.

Successive international efforts -- led by regional bloc IGAD -- have so far failed to impose a functioning peace deal or meaningful ceasefire.

Abiy "will call upon the two leaders to narrow their gap and work for the pacification of South Sudan," Meles said.

Tens of thousands have died and nearly four million South Sudanese have been driven from their homes since December 2013, while millions are going hungry amid a massive humanitarian crisis.

Last month the UN Security Council gave the warring sides a month to reach a peace deal or face sanctions.