CAIRO/DUBAI — The United States on Tuesday said it had reimposed a naval blockade of all Iranian ports in the latest escalation in the conflict, while President Donald Trump dropped a 20 percent transit fee on shipping through the Strait of Hormuz he had pitched only a day earlier. The U.S. also began a fresh round of strikes "to continue degrading Iranian capabilities used to attack commercial shipping in the Strait of Hormuz," the U.S. military said. Tehran has again closed the strait after hostilities between Iran and the U.S. reignited last week, fraying an already fragile truce reached in June after several months of fighting that has killed thousands. Over the last day, Iran has struck U.S. facilities in Jordan and Bahrain, while United Arab Emirates-owned shipping tankers were hit in the strait. The renewed attacks have increased doubts that a memorandum of understanding signed last month would lead to a permanent halt in the war, which has engulfed Iran's neighbors and disrupted global energy supplies. Prior to the war's outbreak in February, the strait was used to transit ab