The United Nations envoy who had tried to avert a conflict in Yemen said Wednesday that he wants to resign, following vocal criticism of his four years of fruitless diplomacy.

The envoy, Jamal Benomar, said in an interview at The New York Times that he had already expressed his desire to Secretary General Ban Ki-moon.

Stéphane Dujarric, a spokesman for Mr. Ban, said Mr. Benomar “has expressed an interest in moving on to another assignment.”

He added: “A successor shall be named in due course. Until that time and beyond, the United Nations will continue to spare no efforts to relaunch the peace process in order to get the political transition back on track.”