Trump said he had walked away from a nuclear deal at the summit with North Korea’s leader Kim Jong-un, because of unacceptable demands to lift US-led sanctions.

North Korea’s foreign minister said that Pyongyang had offered to permanently dismantle all its nuclear material production including plutonium and uranium, observed by US experts.

But the minister said Washington insisted Pyongyang take one more step beyond dismantling its Yongbyon nuclear complex.

He did confirm that North Korea asked Washington to partly lift US-led sanctions.

Trump soon announced the summit was over and no deal had been made, and a scheduled lunch was cancelled.

“Sometimes you have to walk,” Trump said at a closing news conference.

It was a dramatic reversal for a summit that had kicked with friendly greetings, laughter and lots of arm-touching by Trump at a luxury hotel.

Kim likened the scene of the two leaders, who had once denounced one another as “Little Rocket Man” and “deranged”, sitting side by side to a “fantasy movie”.

The two men met privately in the morning for about 35 minutes and were then joined by US Secretary of State Mike Pompeo and his North Korean counterpart.

The four, plus two interpreters, spoke for about 70 minutes in what was described as an “informal” session.

Trump and Kim took a 15-minute break and then reconvened, this time with more officials.

Pompeo said later that US officials had been hopeful for a deal even on Thursday morning after working through the night.

“We all went back and tried to sharpen our pencils and see if we couldn’t get a little further and we actually did,” he told reporters on his plane.

But not far enough.

Next on the schedule was the lunch that never happened, followed by a signing ceremony for a joint agreement that was advertised on Trump’s public schedule. But there was nothing to sign.

Air Force One took off two hours early as Trump left for Washington without a deal.

–with AAP