WASHINGTON — U.S. President Donald Trump threatened on Monday to hit Iran "hard" after the two foes traded fire for the first time in weeks, as his Treasury secretary vowed to keep up a pressure campaign aimed at hobbling Tehran's economy. After six months of war, the foes remain at an impasse, with Iran keeping the strategic Strait of Hormuz closed and the U.S. persisting with a counter-blockade of Iranian ports. On Sunday, the United States carried out strikes on an Iranian island in the Strait of Hormuz, with Tehran quickly retaliating by attacking U.S. military targets in the Middle East. The exchange raised fears of a return to major hostilities, with the U.S. president vowing to respond. "We're going to hit them hard," Trump said, according to a Fox News reporter who spoke to him briefly. "There will be a response." The United States said it attacked Iranian rocket launchers on the island of Larak to prevent Tehran planting mines in the key shipping lane. Iran responded with missile and drone attacks aimed at Jordan and the United Arab Emirates, saying they targeted U.S. forces the