US President Donald Trump tweeted on Saturday that he hoped for a "truly wonderful result" coming out of his first meeting with the Democratic People's Republic of Korea's top leader Kim Jong-un in Singapore on Tuesday.

"I am on my way to Singapore where we have a chance to achieve a truly wonderful result for North Korea and the World. It will certainly be an exciting day and I know that Kim Jong-un will work very hard to do something that has rarely been done before, create peace and great prosperity for his land," Trump said on his Twitter account.

"I look forward to meeting him and have a feeling that this one-time opportunity will not be wasted!" the president tweeted.

Trump had just attended the Group of Seven summit in Canada. He told reporters after the G7 meeting early on Saturday that he would be leaving for Singapore "on a mission of peace".

"So we're going in with a very positive attitude, and I think we're going to come out fine," Trump said, according to a release from the White House.

"But I've said it many times: Who knows? Who knows? May not. May not work out. It's a good chance it won't work out. There's probably an even better chance that it will take a period of time. It will be a process."