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(CNN) —  

President Donald Trump sounded an optimistic note Saturday morning about his upcoming summit with North Korean leader Kim Jong Un, but called the meeting a “one-time shot” for Kim.

“I feel that Kim Jong Un wants to do something great for his people,” Trump said. “And he has that opportunity, and he won’t have that opportunity again.”

Trump was speaking from the G7 summit in Canada ahead of his trip to Singapore for the planned sit-down with the North Korean dictator. Calling his trip “a mission of peace,” the US President framed the meeting as a rare opportunity for Kim and said the US was going in with a positive outlook.

At the same time, Trump said there was a “good chance” the meeting would not work out and claimed he would know almost immediately after the start of talks how the situation would progress.

“I think within the first minute I’ll know,” Trump said.

Trump acknowledged uncertainty around the highly anticipated summit, saying he was bolstered by discussions in the run-up to the meeting and would not guarantee a specific outcome from the talks.

“So far so good,” Trump said. “We’re going to have to see what happens.”

Trump said at the least, he hoped the meeting would start a dialogue and a direct understanding between himself and the reclusive leader of North Korea.

“At a minimum, I do believe, at least we’ll have met each other,” Trump said, adding later that “hopefully, we will have liked each other.”

While en route to Singapore later Saturday, Trump said he looked forward to meeting Kim on what he anticipated would be an exciting day.

“I am on my way to Singapore where we have a chance to achieve a truly wonderful result for North Korea and the World,” Trump wrote in a pair of tweets. “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. I look forward to meeting him and have a feeling that this one-time opportunity will not be wasted!”

Vice President Mike Pence said at a Christian nonprofit organization’s conference in Washington, DC, on Saturday that he had spoken with Otto Warmbier’s father earlier in the day and that Trump was going into the summit with “with the family of Otto Warmbier on his heart.”

The 22-year-old American student was detained in North Korea for 17 months and was returned to his family “with severe brain damage and in a nonresponsive state” last June. He died later that month.

Pence also said at the Faith and Freedom Coalition conference that Trump is approaching the summit with confidence.

“The truth is, he’s been preparing for this his whole life,” Pence said. “The President truly believes that Kim Jong Un, in the President’s words, wants to do something great for his people. As the President often says, we’ll see what happens.”

The summit is set to mark the first meeting between a sitting US President and a North Korean leader and comes after Trump and Kim previously engaged in a war of words over the North Korean nuclear program and each nation’s military capabilities.

Sources told CNN that US officials have established a contingency plan for a potential second day of discussions between Trump and Kim depending on the direction of their planned meeting on June 12.

Trump said Saturday that once they met, he would know for how long to continue talks and whether it would amount to a waste of time to go forward.

“I think I’ll know pretty quickly whether or not, in my opinion, something positive will happen,” Trump said. “And if I think it won’t happen, I’m not going to waste my time. I don’t want to waste his time.’

CNN’s Alessia Grunberger, Jeremy Diamond and James Griffiths contributed to this report.