SEOUL, South Korea (AP) — North Korean leader Kim Jong Un has said an elevated U.S. security partnership with South Korea and Japan poses a grave threat to his country and vowed to further bolster his nuclear weapons program. Kim has previously made similar warnings, but his latest statement implies again that he won’t likely embrace President Donald Trump’s overture to meet him and revive diplomacy anytime soon. State media said Sunday that Kim called a U.S. push to boost a trilateral military partnership with Japan and South Korea a “grave” security challenge. Kim was cited as reaffirming “the unshakable policy of more highly developing the nuclear forces.”