Conflict erupted in South Sudan in December when President Salva Kiir accused former Vice President Riek Machar of trying to overthrow the government.
Toby Lanzer, the U.N. humanitarian coordinator for South Sudan, told the U.N. News Center fighting was ongoing and the situation was dire.
"People are crying out for help," he said in an interview published Wednesday. "We're at a really desperate moment in South Sudan."
Africa's Intergovernmental Authority on Development, which led South Sudanese peace talks, said Tuesday it called on all parties to the conflict to show their "political will and commitment to end the war."
The United Nations estimates "thousands" of people died as a result of the conflict and an estimated 870,000 people were forced to flee their homes since fighting erupted mid-December.
Despite IGAD's mediation, Lanzer said the people of South Sudan are frightened for their future.
"We need a cease-fire that works, that works for civilians on the ground; that enables them to move, to go back to their homes, to look after their livestock, to plant and to cultivate," he said.