The leader of United Nations’ peacekeeping operations offered a dire appraisal of South Sudan on Tuesday, saying the world’s youngest nation is sliding further into mayhem with no sign that its antagonists want peace.

In a report to the United Nations Security Council, Jean-Pierre Lacroix, the under secretary general of the Department of Peacekeeping Operations, called upon the leaders of South Sudan’s warring factions to “bring the country back from the impending abyss.”

Mr. Lacroix said that a diplomatic effort by eight African nations to revitalize a 2015 peace agreement in South Sudan had received only a “lukewarm response” from the government of President Salva Kiir, and that Mr. Kiir’s political adversaries also remained cautious about it.

Despite the presence of 17,000 United Nations peacekeepers in South Sudan, Mr. Lacroix said that security had deteriorated and that armed clashes, extrajudicial killings, arbitrary arrests and other rights abuses had increased in much of the country.