The United States on Tuesday launched a multinational operation to safeguard commerce in the Red Sea as attacks by Iran-backed Yemeni militants forced major shipping companies to reroute, fuelling concern over sustained disruptions to global trade. The Houthi group, which controls vast amounts of territory in Yemen after years of war, has since last month fired drones and missiles at international vessels sailing through the Red Sea - attacks it says respond to Israel's devastating assault on the Hamas-ruled Gaza Strip.