"As you know, I will be meeting with the president of China very soon in Florida, and that's another responsibility we have and that's called the country of North Korea. We have a big problem. We have somebody that is not doing the right thing," Trump said.

"That's going to be my responsibility, but I will tell you that that responsibility could have been made a lot easier if it was handled years ago," he said, repeating his criticism of his predecessor former President Barack Obama for mishandling security and economic problems.

It was the latest in a series of remarks Trump made about the North in the run-up to the summit with Xi.

On Tuesday, Trump called the North a "humanity problem" and said it will be a key topic for talks with Xi.

"We're going to have a great meeting. I'm sure we're going to have a fantastic meeting and we're going to talk about a lot of things, including, of course, North Korea, a problem, and that's really a humanity problem," Trump said during a townhall meeting with business CEOs.

Earlier, Trump said in an interview published Sunday that China should help with the North Korea problem by using the "great influence" it has over Pyongyang, warning that if it doesn't, the US will solve the problem on its own, and that won't be good for anyone.

Trump also said he will use trade as an incentive for China to take action on the North.