WASHINGTON (AFP/REUTERS) - US President Donald Trump said Friday (June 1) his summit with North Korea’s leader Kim Jong Un is back on for June 12, after extraordinary Oval Office talks with a top envoy from Pyongyang.

Trump emerged after a more than hour-long meeting with Kim Yong Chol – a general facing US sanctions who is Kim’s right-hand man – saying that the summit will go ahead in Singapore as originally planned.

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While admitting that dealing with North Korea was “going to be a process,” Trump said he believed that process would ultimately be “successful”.

“They want it. We think it's important. I think we would be making a big mistake if we didn’t have it." he told reporters. "I think we're going to have a relationship and it will start on June 12.”

Trump said the letter from Kim, hand-delivered by Kim Yong Chol, was “very nice” and “very interesting” – but then said he had not opened it yet.

Nevertheless, the US president had warm words for Pyongyang, saying the long discussions had touched on North Korea’s denuclearisation and economic development.

Trump indicated that the campaign of “maximum pressure” was at least on hold, vowing no new sanctions while talks are ongoing.

“The relationships are building and that’s very positive,” he said. In a move that is sure to worry US allies in Japan and South Korea, Trump also said that he and his guest had discussed US troop numbers on the Korean peninsula.

.@realdonaldtrump: "We're meeting with the Chairman on June 12th..." pic.twitter.com/b0sEBbTkPf — The White House (@WhiteHouse) June 1, 2018

“We talked about almost everything. We talked about a lot. And we talked about sanctions,” he said.

Trump appeared to significantly lower expectations for the outcome of the historic summit, frequently describing it as the start of a process and not the place where the two leaders were likely to sign any agreement.

He said a number of summits might be required.

“Frankly, I said, ‘Take your time,’” Trump said.

It was an extraordinary softening of tone toward North Korea from a president who last year threatened to rain “fire and fury” on the country because of the threat its nuclear weapons and long-range missiles pose to the United States.

After exchanging threats and insults since Trump became president last year, the United States and North Korea have been trying to set up the summit between their leaders. Trump wants to use the meeting to pressure Pyongyang into giving up its nuclear weapons.

Wall Street took word from Trump that the summit was back on in stride. The S&P 500 added slightly to what were already healthy gains, then slipped back a few points to remain up 0.9 per cent in afternoon trade. The US dollar index added modestly to a gain.

North Korea, whose nuclear ambitions have been a source of tension for decades, has made advances in missile technology in recent years but Trump has sworn not to allow it to develop nuclear missiles that could hit the United States.

He wants North Korea to “denuclearise,” meaning to get rid of its nuclear arms, in return for relief from economic sanctions but the leadership in Pyongyang is believed to regard nuclear weapons as crucial to its survival and has rejected unilaterally disarming.

“I look forward to the day when I can take the sanctions off of North Korea,” Trump said.

Trump had called off the summit late last month, citing North Korea’s “tremendous anger and open hostility.”