A Houthi drone boat laden with explosives detonated in the Red Sea on Thursday but failed to cause any damage or casualties, the US Navy said, as the Yemen-based group continued its attacks in defiance of international calls to stop. The latest attack came one day after 12 countries, including the United States, Britain, and Japan, issued a joint statement cautioning the Houthis of unspecified “consequences” unless it halts its attacks, in what one US official on Wednesday suggested was a final warning. The Iran-aligned Houthis, who control much of Yemen, have launched wave after wave of exploding drones and missiles at commercial vessels since November 19, trying to inflict a cost in what they say is a protest against Israel’s military operations in Gaza. The Houthi campaign has been extraordinarily disruptive to international shipping, causing some companies to suspend transits through the Red Sea and instead take the much longer, costlier journey around Africa. Vice Admiral Brad Cooper, who leads US Naval forces in the Middle East, told reporters on Thursday that the Houthi exploding boat drove out about 50 miles into the Red Sea and then detonated in dense shipping lanes. “It came within a couple of miles of ships operating in the area — merchant ships and US Navy ships — and we all watched as it exploded,” Cooper told reporters, adding the target of the attack was not clear.