Yemeni fighters from the Houthi movement said they will seal off Saudi Arabia’s coast starting Monday. Their spokesman, Yahya Saree, called it a naval attack. Oil tankers moving through the Red Sea near Saudi ports could face delays. U.S. warplanes kept hitting targets after their warning. The group seized several ships. Insurers now see Red Sea routes as hazardous. Traders are waiting anxiously, watching for additional charges or rerouted cargo. Saudi ports are close to the danger zone, so any delay is critical quickly.