Trump says received 'positive letter' from N Korean leader Kim Jong-un

US President Donald trump on Saturday said he has received a "positive letter" from North Korean leader Kim Jong-un, with whom, he describes, has developed a good relationship.

Trump, however, refused to divulge the details of the letter.

He said he will have another meeting with Kim.

Beginning last summer, Trump and Kim have met three times and the major focus of their talks has been the denuclearisation of the Korean Peninsula.

"I think we'll have another meeting. He really wrote a beautiful, three-page -- I mean, right from top to bottom -- a really beautiful letter. Maybe I'll release the results of the letter, but it was a very positive letter," Trump told reporters at the White House.

Responding to a question, he said that the North Korean leader "was not happy with the missile testing".

"He gave me a great letter. I would love to give you, but, I don't know, I don't think it would be appropriate. But it was a very personal letter. It was a great letter. He talked about what he's doing. He's not happy with the testing. It's a very small testing that we did," Trump said.

"But he (Kim) wasn't happy with the testing; he put that in the letter. But he also sees a great future for North Korea. We will see how it all works out," he added.

Trump said there has been been no nuclear tests in North Korea, but short-range missile tests.

"No ballistic missile tests. No long-range missiles. We are getting back a lot of our fallen heroes. They're coming back into and through Hawaii. And we got back our hostages," he said.

The US President said the letter was hand-delivered to him and was not "touched by anybody".

"They literally take it from North Korea to my office. We have a system. It's the old-fashioned system. You don't have to worry about leaks. Something nice about that system," he said.

"He (Kim) wasn't happy with the war games. The war games on the other side, with the United States," Trump said.

"As you know, I've never liked it either. I've never liked it. I've never been a fan. You know why? I don't like paying for it. We should be reimbursed for it, and I've told that to South Korea.

"But I don't like it either. But I said, 'Do this', because this was a big test. This was a turnover of various areas to South Korea. I like that because that's what should happen," he said.