U.S. naval forces in the Red Sea this month boarded a freighter suspected of delivering Iranian weapons to Houthi rebels in Yemen, American military officials said.

The destroyer USS Sterett’s search of the Panamanian-flagged Saisaban on April 1 came up empty. But the officials said it marked the U.S. Navy’s first boarding operation in an expanding campaign to ensure Iran doesn’t supply game-changing weapons such as surface-to-air missiles that would threaten Saudi-led airstrikes on the Houthis.

The airstrikes began two weeks ago after Houthi rebels, who have taken over the capital and overrun much of the country, forced American-backed President Abed Rabbo Mansour Hadi to flee the country. […]