Seoul (AFP) – Before President Joe Biden left South Korea for Japan Sunday, he offered a brief message to Kim Jong Un, whose nuclear sabre-rattling has risked overshadowing the US leader’s first Asia trip: “Hello. Period.” He offered the succinct greeting when reporters asked whether he had anything to say to North Korea’s leader, highlighting his administration’s openness to dialogue with Pyongyang, even as they look to ramp up joint military exercises with South Korea. Biden said that he was “not concerned” about the risks of a fresh weapons test while he was in the region — something US of…