United Nations chief Ban Ki-moon called Thursday for an immediate halt to the fighting in Yemen, as he began the hunt for a new UN envoy who can broker a political end to the conflict.
Yemen "is in flames," the secretary general told a National Press Club dinner in Washington on the sidelines of International Monetary Fund and World Bank spring meetings.
"I am calling for an immediate ceasefire in Yemen by all parties," he said.
"It is time to support corridors for lifesaving aid and a passage to real peace," Ban said.
"The United Nations-supported diplomatic process is the best way out of a drawn-out war with terrifying implications for regional stability."
Ban's remarks followed the resignation of UN envoy Jamal Benomar, as a Saudi-led coalition pressed its air war against Iran-backed rebels in Yemen.
The Moroccan-born career diplomat enjoyed Ban's support, but no longer had the confidence of Saudi Arabia and its allies, amid accusations that he was appeasing the rebel side.
Ban said he was in the process of finding a new envoy for Yemen "who can be immediately deployed" to seek a political solution.
"The Saudis have assured me that they understand there must be a political process," he said.
"I call on all Yemenis to participate, and in good faith," he added.
Houthi rebels overran Yemen's capital Sanaa last September, then put Saudi-backed President Abedrabbo Mansour Hadi under effective house arrest in January.
Hadi's escape to second city Aden in February to rally opposition to the rebels effectively brought negotiations to an end.
Benomar's efforts to revive talks proved fruitless as the rebels advanced on the president's last refuge, triggering his flight to Saudi Arabia.
On Tuesday, the UN Security Council slapped an arms embargo on the Houthi rebels and demanded they give up territory they had seized.
The United Nations has also placed a global travel ban and asset freeze on Houthi leader Abdul Malik al-Houthi and leading rebel backer Ahmed Ali Saleh, son of former Yemeni president Ali Abdullah Saleh.
Ban is in Washington with several of his top advisors for meetings with US officials and finance ministers attending the IMF and World Bank spring meeting.
He discussed issues as varied as Ebola, climate change, Syria and Yemen in meetings with the House of Representatives and Senate foreign affairs committees.
He also lunched with US Defense Secretary Ashton Carter, discussing Yemen as well as an upcoming summit on UN peacekeeping, Ban's spokesman said.