UNITED NATIONS — The U.N. special envoy for Yemen warned Wednesday that conflict in the Arab world’s poorest nation is intensifying daily, with terrorist groups expanding, 14 million people in desperate need of food and the worst cholera epidemic in the world.

Ismail Ould Cheikh Ahmed called on all parties “to act for the sake of peace,” stressing that “their excuses are unacceptable and their justifications are unconvincing, especially when the solutions are in plain sight.”

“The opportunity to reach peace is not yet lost,” he told the Security Council. But “the political leadership must recognize that the continuation of the war can only lead to more human and physical loss, and complicate crucial questions on the future of the country, including the grievances of the south.”

Yemen, which is on the southern edge of the Arabian Peninsula, has been engulfed in civil war since September 2014, when Houthi Shiite rebels swept into the capital of Sanaa and overthrew President Abed-Rabbo Mansour Hadi’s internationally recognized government.

In March 2015, a Saudi-led coalition, backed by the United States, began a campaign against Houthi forces allied with ousted President Ali Abdullah Saleh in support of Hadi’s government. Since then, the Iranian-backed Houthis have been dislodged from most of the south, but remain in control of Sanaa and much of the north.

In the southern part of the country, the United Arab Emirates, which is part of the Saudi-led coalition, has set up its own security forces, running virtually a state-within-a-state and fueling the south’s independence movement.

U.N. humanitarian chief Stephen O’Brien said the warring parties and their outside backers should feel “deeply guilty” at driving a worsening conflict that has exposed millions of Yemenis civilians “to unfathomable pain and suffering” – including 7 million people now “on the cusp of famine.”