WASHINGTON - US President Donald Trump, arriving back in the United States on Wednesday after his historic summit with North Korean leader Kim Jong Un, said Pyongyang no longer posed a nuclear threat."Everybody can now feel much safer than the day I took office. There is no longer a Nuclear Threat from North Korea. Meeting with Kim Jong Un was an interesting and very positive experience. North Korea has great potential for the future!" Trump wrote on Twitter.North Korea also was no longer the United States' "biggest and most dangerous problem," he added.