Haysom said South Sudan's leaders have done very little to implement the country’s roadmap for the extension of the transitional period.
In August 2022, the signatories to the 2018 peace deal extended the transitional period by another two years, arguing that additional time was needed for completion of some key elements of the agreement.
The UNMISS cheif told reporters the constitution making process, by estimation, is 10 months behind schedule and election planning is eight months behind schedule.
"Several aspects of the transitional security arrangement are simply hanging," he said.
Haysom said he met President Salva Kiir and expressed concerns over the slow progress in the implementation of the roadmap.
"At the beginning of the year, I outlined challenges facing South Sudan. We still see the year 2023 as a make-or-break year for this nation if it is to fully implement the peace agreement which is to suggest matters cannot be deferred to 2024."
Puok Both Baluang, director for communications for the Sudan People Liberation Movement In Opposition, a main signatory of the 2018 peace deal, told VOA several factors contributed to the slow implementation of the road map.
"Lack of political will, lack of the role of guarantors of the agreement to carry out their duties, to supervise and to make sure that the agreement is implemented in letter and spirit and then we add the issue of lack of resource," Buluang said.
Buluang challenged the U.N. to play a major role rather than "point fingers to the parties."
Haysom said the rates of violence and human rights abuses are still up in South Sudan.
"Unfortunately, human rights bodies have recorded violations in various parts of the country and the first quarter report showed a 12% increase in violence incidents affecting civilians compared to the same reporting period last year," Haysom said. He added minimal steps have been taken by authorities to hold perpetrators accountable.
South Sudan's cabinet minister and Secretary-General for the High Level Implementation Committee of the Peace Agreement, Martin Elia Lomuro, told VOA that the signatories of the peace deal are working hard to implement the roadmap.
"Haysom is in a hurry. The government and UNMISS agreed on a joint task force that will be dealing with the electoral and constitutional making process," Lomuro said.
Lomuro accused UNMISS of doing "very little" to support the peace process in the nation.
"We just had a conference on Chapter Five and they contributed zero. They just talk. We have formed a task force and we shall see what they can do," Lomuro said.
South Sudan is scheduled to hold first elections as an independent country in 2024.