Yemeni fighters from the Houthi movement said they will block Saudi Arabia’s coast starting Monday. Their spokesman, Yahya Saree, dubbed it a naval attack. Merchant ships moving through the Red Sea near Saudi ports could face delays. U.S. warplanes persisted in attacking targets after their warning. The group seized several ships. Insurers now see Red Sea routes as hazardous. Traders are watching closely, watching for extra costs or alternative loads. Saudi ports border the threatened zone, so any delay is critical quickly.