South Sudan President Salva Kiir has threatened to form a unity government without opposition leader Riek Machar if he does not return to the country soon.

He gave the warning during prayers being hosted at State House in the capital, Juba, to mark one year since the signing of a peace deal.

The agreement, which ended a five-year civil war that killed tens of thousands of people, forced millions from their homes and devastated the economy, sets a November 2019 deadline to set up a joint government.

“I want to promise you that in November the national unity government must be formed. If the armed opposition does not want to form a government, we will go ahead with the other signatory parties to form the government on time,” Mr Kiir said.

Last week, the two rivals held their first face-to-face talks in months in Juba and said progress was being made on forming the government, though some issues still needed to be sorted such as security arrangements.

But on Thursday Kiir urged his rival to return "well in advance" of November for the negotiations to continue.

“Even if he comes in October, I have no problem, let him come,” the president said.

A similar peace deal, signed in 2015, fell apart a year later in deadly clashes in Juba that saw Mr Machar flee into exile.

However, Kiir sought to calm the nerves of the opposition saying that when Mr Machar returned for last week’s negotiations, he could see there was nothing to worry about.

“He saw it when he came here nobody was against him and this is the place where they embarked on fighting last time, but nobody was against him, I received him with open arms and with open heart,” the president said.

Anglican Archbishop Justin Badi Arama also addressed the prayer gathering and urged all rivals to come together in peace.

“Do not dwell on the past - in the past you did all evil but today the Lord is saying, 'Forget the past, just embrace love.' When we say, ‘Love your neighbour’ – that person is from another tribe, love him or her.”

Earlier this week, a group of UN experts warned that the country risks being plunged back into full-scale conflict if hardliners are allowed to sabotage the peace agreement.