Washington (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.

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