Yemen's internationally recognized government pressed world leaders on Thursday for help defeating the Houthi rebels, saying the group's new positions along a key waterway present an international economic risk. The Houthis, who have controlled Yemen's capital, Sanaa, and much of the country's north for over a decade, moved down Yemen's coast this month and seized the port city of Mokha and key Red Sea islands. That gives them better surveillance of ships passing through the Bab el-Mandeb Strait, at the southern end of the Red Sea. About 12% of the world's trade usually passes through the waterway. The rebels have declared a blockade on Saudi shipping. While asserting there is no other threat to commercial shipping on the Red Sea, they have not detailed further actions in the supplied account. Yemen's government describes the Houthis as Iran-backed.