US President Joe Biden on Friday called Yemen's Houthi forces a "terrorist" group, after American and British warplanes, ships and submarines launched dozens of air strikes across Yemen overnight.
Biden said Washington will respond to the Houthis if they continued behavior that he called outrageous.
London and Washington say their airstrikes in Yemen, most of which is controlled by the Houthis, were in retaliation for months of attacks by the movement on Red Sea shipping that the Iran-backed fighters cast as a response to the ongoing war in Gaza.