CAIRO (AP) — The U.S. military launched the 13th night of strikes Thursday against Iran, targeting key military and commercial sites as clashes continued to escalate over shipping routes. Meanwhile, the Houthis threatened to shut down another key trade route, with the world economy already reeling from Iran's closure of the Strait of Hormuz. Iran and the U.S. have stepped up attacks as they vie for control of the strait, setting off a scramble for alternative routes. President Donald Trump threatened "major military punishment" against the Houthis if their attacks on ships continue. "If they do this again, the U.S. will hold Iran responsible, in that the Houthis are a Surrogate and/or Proxy of Iran, and major military punishment will be inflicted upon Iran and, of course, the Houthis, themselves," Trump wrote on social media.