WASHINGTON - US President Donald Trump said on Thursday that Pyongyang is a problem that "will be taken care of," as speculation rose that North Korea might be on the verge of a sixth nuclear test.Trump, responding to a question about what his message is for North Korea, said, "North Korea is a problem. The problem will be taken care of."He said he believed Chinese President Xi Jinping would "work very hard" to help resolve the challenge. The president said he had spent a lot of time with Xi last week in Florida."I have really gotten to like and respect President Xi. ... He's a very special man. I think he's going to try very hard."