South Korea and the United States staged their first combined military exercises involving an American aircraft carrier in more than four years, Seoul’s military said on Saturday, amid reports that North Korea was preparing for a nuclear test. The three-day drills took place in international waters off the Japanese island of Okinawa until Saturday, including air defence, anti-ship, anti-submarine, and maritime interdiction operations, South Korea’s Joint Chiefs of Staff said. The exercises came amid signs that North Korea is gearing up to conduct a nuclear test for the first time since 2017. Seoul officials have said Pyongyang has conducted multiple experiments with a detonation device in preparation for its seventh underground explosion. The USS Ronald Reagan, a 100,000-ton nuclear-powered aircraft carrier, joined the drills, alongside the guided-missile cruiser USS Antietam, the Aegis-equipped USS Benfold destroyer, and the Fleet replenishment oiler USNS Big Horn, the JCS said. South Korea also sent the 14,500-ton Marado amphibious landing ship, the 7,600-ton Sejong the Great destroyer, and the 4,400-ton Munmu the Great destroyer, among others. It was the allies’ first joint military exercise since South Korea’s President Yoon Suk-yeol took office last month, and their first bilateral exercises involving an aircraft carrier since November 2017.