Will walk out if meeting with Kim doesn't go well: Trump

US President Donald Trump has expressed optimism about his planned summit with North Korean leader Kim Jong-un, but said he'd be willing to walk out if the meeting fails to meet his expectation.

Trump said he will be meeting with Kim Jong-un in the coming weeks to discuss the de-nuclearisation of the Korean Peninsula.

"If we don't think it's going to be successful.. we won't have it. We won't have it. If I think it's a meeting that is not going to be fruitful, we are not going to go," Trump told reporters during a joint news conference with Japanese Prime Minister Shinzo Abe at Mar-a-Lago in Florida.

"If the meeting, when I'm there is not fruitful, I will respectfully leave the meeting and will continue what we are doing or whatever it is that we'll continue, but something will happen," Trump said a day after he told reporters that he is likely to meet Kim Jong-un in June or before that.

Officials from the two countries are looking at five different venues for the meeting. None of them are in the US.

"Hopefully, that meeting will be a great success and we're looking forward to it," Trump said, adding that it would be tremendous for the world if the meeting went well.

Trump expressed hope that the Korean Peninsula could live together "in safety, prosperity, and peace" following a series of meetings between North Korea and South Korea.

"This is the destiny of the Korean people, who deserve and have gone through so much over the years. We hope it all works it and we'll be trying very hard," he added.

Trump said the release of three American prisoners in North Korea would be among the topics of his discussion with Kim.

The US president pat himself on the back over North Korea and said his administration had achieved what his predecessors couldn't.

"..for many years they have been talking to North Korea and nothing has happened. This should have been taken care of by past administrations when they were not nearly so far along. But we put unbelievably powerful sanctions on, and many other things," said Trump.

He praised Chinese President Xi Jinping for co-operating with him on North Korea.

"He has plugged up the border, and he's done it very, very powerfully. He would tell you himself that he never thought he would go to this extent. And I appreciate that very much," he said.

"..He (Xi) doesn't want to see a North Korea, or any Korea that has nuclear weapons either. So, he's also fighting for China when it comes to this but he has been terrific. Can he be better? I always say yes, he can be better," he added.

Trump also said that it was his involvement and that of the US that made 'PyeongChang 2018 Olympic Winter Games' "a great success".

"If you look at ticket sales prior to what took place with respect to North Korea, it was going to be a big problem, and it turned out to be a very successful Olympics. So we've gotten us here, and I think were going to be successful. But if for any reason I feel were not, we end," Trump said.

Abe extended his support towards Trump for his efforts regarding North Korea and demanded complete denuclearisation of North Korea.

"Based on such (past) lessons learned, both the US and Japan, together with the international community will demand for all weapons of mass destruction of ballistic missiles complete verifiable and irreversible dismantlement of weapons of mass destruction and ballistic missiles to North Korea," Abe said.

"By envisioning multiple scenarios, we carefully thought out our policies and directions at a concrete and detailed level. Just because North Korea is responding to dialogue there should be no reward," Abe said.

The Japense prime minister demanded that maximum pressure be maintained and actual implementation of concrete actions toward de-nuclearisation be demanded from North Korea.

Abe said in his talks with Trump, the two countries have reached agreement regarding the upcoming US-North Korea summit.

"We hope that it will lead to the resolution of weapons of mass destruction, nuclear missile, and of course, more than anything else we hope it will be historic summit that will lead to the resolution of abduction," he said.