On May 12th, opposition leader Machar is expected to return to South Sudan and once again serve as Kiir's deputy.
Pope Francis, on Thursday kissed the feet of South Sudan's rival leaders at the close of a 2-day retreat in the Vatican for the African leaders.
South Sudan's civil war has left 2.1 million people internally displaced, with another 2.5 million refugees, according to the United Nations.
The Pope said the people of South Sudan are exhausted of conflicting and they yearn for unity and peace.
The pope was there for the two leaders and three other vice presidents to uphold an armistice they signed to form a unity government next month. But the two leaders slipping away the longer the more in control of their areas - many of its combat troops have now self-conscious Warlords at the top, which act more and more independently and financially from the civil war to profit, because they exploit the rich mineral resources of the country on their own.
Closing his prepared remarks with a prayer, he asked God "to touch with the power of the Spirit the depths of every human heart, so that enemies will be open to dialogue, adversaries will join hands and peoples will meet in harmony".
"The objective of this retreat is for us to stand together before God and to discern his will", he said in his formal remarks on Thursday, closing the two-day retreat in the Domus Sanctae Marthae, the Vatican guesthouse where he lives.
Trump considered Ivanka for WB
Ivana Trump revealed the truth on how her daughter Ivanka really feels about her stepmom and First Lady, Melania Trump. If he did nominate her , Mr Trump said, "they'd say nepotism, when it would've had nothing to do with nepotism".
Kiir and Machar signed a tenuous peace agreement in September 2018, which the country's Catholic bishops have called "fatally flawed" because it does not address the root causes of the conflict.
Diplomats and experts agreed that it would be hard to meet the deadline.
"Peace is the first gift that the Lord brought us, and the first commitment that leaders of nations must pursue", he told them.
"I don't think it's cynical, it's practical".
Machar also said he is confident that the new military leadership in Khartoum will continue to be "a strong guarantor" of the fragile South Sudan peace deal.
Sudan, a largely Muslim nation, granted the largely Christian south its independence in 2011 after decades of scorched-earth fighting.
South Sudan has been at conflict nearly since splitting from Sudan which ended Africa's longest running civil war.