As Houthi attacks roil the Red Sea and Western air raids target the rebels, moves to end Yemen's long-running war are at a standstill, threatening further woe for a country on its knees.

As recently as December, painstaking negotiations were gaining ground and the United Nations said the warring parties had agreed to work toward "the resumption of an inclusive political process."

The Iran-backed Houthis have been fighting a Saudi-led coalition since March 2015, months after they seized the capital Sanaa and most of Yemen's population centers, forcing the internationally recognized government south to Aden.