UNITED NATIONS — The U.N. humanitarian chief is warning that conditions in Yemen are “catastrophic” after three years of war, with 22.2 million people needing aid. And the U.N. envoy is accusing both the Saudi-backed government and Shiite rebels of prolonging the conflict.

The U.N. officials painted a dire picture of the Arab world’s most impoverished country plunging into the world’s worst humanitarian crisis and facing massive destruction as a result of what special envoy Ismail Ould Cheikh Ahmed called the parties’ continuing “destructive pattern of zero-sum politics.”

Undersecretary-General for Humanitarian Affairs Mark Lowcock warned the Security Council that “famine remains a real threat.”

Cheikh Ahmed disclosed that a peace agreement had been about to be reached, but the parties refused to sign at the last minute. He called for fresh negotiations.