The United Nations' top official in Yemen warned Monday that Yemen will remain a powder keg for renewed war unless its rival factions work out a new cease-fire deal.

Hans Grundberg, the U.N. special representative for Yemen, said that the situation in the conflict-stricken country is fragile nearly a year after the internationally recognized government and the Iranian-backed Houthi rebels failed to renew a U.N.-brokered cease-fire.

The conflict has been restrained since then, with only sporadic clashes, but Grundberg said a resumption of all-out fighting is a threat.

“The risk of a flare-up is always there,” he said. “The situation remains fragile and will remain fragile until we have reached an agreement that offers a cease-fire agreement.”

The end to the cease-fire arrangement was a blow to U.N. efforts to find a negotiated settlement to the conflict, which has devastated the country and created one of the world’s worst humanitarian disasters.

Yemen’s war began when the Houthis descended from their strongholds in northern Yemen and seized the capital of Sanaa in 2014, forcing the government to flee to the south and then into exile in Saudi Arabia. The Saudis entered the war in 2015, heading a military coalition that sided with the government and the conflict became a proxy war between Saudi Arabia and Iran.

Speaking after meeting with Egyptian Foreign Minister Sameh Shoukry in Cairo, Grundberg noted Yemen's warring parties have separately been involved in peace efforts in recent months, but he said more effort is needed to establish a firm nationwide cease-fire and restart political talks on ending the conflict.

The envoy welcomed international and regional efforts to end the conflict, including direct discussions between Saudi Arabia and the Houthis. He said such efforts would help the U.N. to craft a proposal for a nationwide cease-fire and the start of political talks between Yemeni factions to end the war.

“The fact that there is direct discussions ongoing between the Houthis and the Saudis can be of support ... to the U.N. mediation efforts,” he said.

The Saudi-Houthi talks gained momentum after Saudi Arabia reached an agreement with Iran last March to restore diplomatic ties after a seven-year rift. The two sides reached a draft deal to revive a cease-fire and usher in a return to direct Yemeni political talks under the auspices of the United Nations, according to Saudi and Houthi officials.