ENTEBBE, Uganda — South Sudan President Salva Kiir and rebel leader Riek Machar will hold rare face-to-face talks on Thursday in Uganda as time runs out for the rivals to form a power-sharing government.

Both sides agreed to a Nov. 12 deadline to join forces in a unity government, but unresolved differences over the terms of peace threatens to scuttle the deal and plunge the country back into war, observers have warned.

The two leaders, whose fall out in 2013 sparked a conflict that has left hundreds of thousands dead, have only met a handful of times since inking a truce last September that brought a pause to fighting.

"They are expected to discuss the unresolved issues as well, and Riek Machar will be having a meeting with President Salva Kiir," the president's spokesperson, Ateny Wek Ateny, said about the talks at State House in Entebbe.

Machar's party, the SPLM-IO, said in a statement the meeting would seek progress on issues that have dragged on "without much having been achieved" since the deal was signed more than a year ago.

The US, Britain and Norway — the troika that leads policy towards South Sudan — welcomed the Uganda tete-a-tete as a way of restoring public confidence in the peace process.

"Any unilateral action is against the agreement and the spirit of the peace process," the troika embassies said in a statement on Thursday.

Moving forward would require "establishing a genuine unity government on Nov. 12 in accordance with the commitments made by the parties" in September 2018, it added.

Machar, who lives in exile in Khartoum, has asked for more time so that the impasse, primarily over security and territory arrangements in South Sudan, can be overcome.

The rebel leader warned that if these were not addressed, the country would see a repeat of fighting in 2016, when an earlier peace deal collapsed, worsening the conflict.

Machar, a former deputy to Kiir, was forced then to flee South Sudan on foot under a hail of gunfire, and has only returned home on rare occasions, fearing for his safety.

Kiir says he's ready to form a new government, and has threatened to do it alone.

But the creation of the coalition government has already been delayed once, in May, and parts of the international community fear another extension risks the already tenuous peace accord.

The United States in particular has warned it would reevaluate its relationship with South Sudan if a unity government isn't forged on Nov. 12, and has floated sanctions.

The peace deal has largely stopped the fighting that erupted just two years after South Sudan achieved independence, violence that left nearly 400,000 dead and displaced close to four million people.

The International Crisis Group warned pushing the Nov. 12 deadline at all costs risked this fragile truce.

"External actors could imperil these gains if they push the parties into a unity government that then falls apart or permit Kiir to exclude Machar," the think tank wrote in a report this week.

The United Nations Security Council, in a statement late Wednesday, said fully implementing "all provisions of the peace agreement remains the only path that will set the country towards the goal of peace, stability and development".

A cornerstone of the accord was that fighters from all sides would be gathered into military camps and trained as a unified army — a process dogged by delays and lack of funding.

Little progress has been made on negotiations around state boundaries — another major sticking point.

The European Union, in a statement Thursday, urged the warring parties to demonstrate "genuine will to build peace" and set realistic deadlines for resolving outstanding issues. — AFP