Herve Ladsous, U.N. undersecretary-general for peacekeeping operations, told the 12-member Security Council peace would be a fleeting prospect in South Sudan so long as parties to the conflict evade their security responsibilities.
"Both parties continue to prioritize the pursuit of military gains over talks towards a comprehensive political settlement," he said in his Tuesday address. "The crisis has already affected the security of the region."
Conflict erupted in South Sudan in December when President Salva Kiir accused former Vice President Riek Machar of trying to overthrow his administration. Machar, sidelined when Kiir reshuffled his Cabinet in July, denies the allegations.
The U.N. Mission in South Sudan said fighting was continuing between rival parties. One person was injured this week when a tank shell exploded near a UNMISS compound in Upper Nile state.
Ladsous warned ongoing fighting was posing a threat to South Sudan's neighbors.
More than 700,000 people have been displaced internally since the conflict began.