SEOUL, SOUTH KOREA — North Korean leader Kim Jong Un said he will implement the “toughest” anti-U.S. policy, less than a month before Donald Trump takes office as U.S. president, the country’s state media reported Sunday. Trump’s return to the White House raises prospects for high-profile diplomacy with North Korea. During his first term, Trump met Kim three times for talks on the North’s nuclear program. Many experts however say a quick resumption of Kim-Trump summitry is unlikely as Trump would first focus on conflicts in Ukraine and the Middle East. North Korea’s support for Russia’s war against Ukraine also