Mr Trump's secretary of state, Mike Pompeo, has similarly downplayed what could be achieved at the summit. On Sunday he told Fox News: "We may not get everything down this week, [but] we hope we'll make a substantial step along the way."
In a separate interview, he also appeared to contradict the president's stated view that there is no nuclear risk from Pyongyang.
"Do you think North Korea remains a nuclear threat?" CNN's Jake Tapper asked him.
"Yes," he replied.
"But the president said he doesn't," Mr Tapper said, to which Mr Pompeo responded: "That's not what he said... I know precisely what he said."
In the aftermath of the Singapore summit last year, Mr Trump tweeted that "everybody can now feel much safer than the day I took office. There is no longer a Nuclear Threat from North Korea"
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