U.S. President Donald Trump stated on Tuesday there was a "substantial chance"  over his summit with North Korean Superemo Kim Jong Un that it will not take place as planned on June 12 amid concerns that Kim is opposed to  giving up his nuclear weapons.

Trump lifted up doubts about the Singapore summit in meetings with South Korean President Moon Jae-in, who visited to Washington to push Trump to not let a rare opportunity with the isolated North Korea slip away.

If the summit is cancelled or fails, it would be a main blow to what Trump supporters expect will be the biggest diplomatic feat of his presidency, and a vast distress for the President himself.

"And you know, there's a chance that it will work out. There's a chance, there's a very substantial chance, that it won't work out. I don't want to waste a lot of time and I'm sure he doesn't want to waste a lot of time. So there's a very substantial chance that it won't work out and that's okay. That doesn't mean it won't work out - over a period of time. But it may not work out for June 12th. But there's a good chance that we'll have the meeting," Trump in his address told to reporters at the White House.