Donald Trump on Sunday stepped into North Korean territory, the first time a sitting US president has ever set foot in the former enemy country.

In a historic moment, Trump walked across the concrete blocks dividing North and South Korean territory in the Demilitarised Zone that divides the peninsula, where the two sides fought each other to a standstill in the 1950-53 Korean War.

The two leaders crossed into North Korea side by side.

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The North Korean leader Kim Jong Un responded that his “wonderful” relationship with US President Donald Trump would enable the two longtime enemies to get over obstructions, with their nuclear talks at a stalemate.

“I am convinced our relationship will enable us to overcome barriers standing in the way,” said Kim, adding as the two leaders held talks in the Demilitarised Zone that their close ties enabled a meeting to happen “just overnight”.

President Donald Trump said the meeting was a “great day for the world”.

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The unexpected encounter, only suggested a day earlier by Trump on Twitter, comes with negotiations over the North’s nuclear program in stalemate since the leaders’ last summit in Vietnam in February.

Accompanied by South Korean President Moon Jae-in, an earnest-looking Trump earlier toured an observation post overlooking North Korean territory, with a US military officer pointing out the sights. 

President Donald Trump shakes hands with North Korean leader Kim Jong Un after their meeting.

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After the meeting, Trump told reporters: “This was a great day, very legendary, very historic day.”

He added that negotiations would resume under Secretary of State Mike Pompeo and that it was “not as complicated as people think”.

“When I came into office, it was a fiery mess, bad things were going on. And the end of the other administration was nothing but trouble, that was all that was happening, and you do not report accurately, but that is OK.

“(On) Sunday, history will report accurately.”

North Korean leader Kim Jong-un (L) walks with US President Donald J. Trump (C) and South Korean President Moon Jae-in (R).

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Trump said teams from the US and North Korea would start meetings “over the next two or three weeks” for talks on Pyongyang’s nuclear program.

Negotiators from the two sides will “start a process and we’ll see what happens”.

He also said he had extended an invite to Kim Jong Un to the White House but there was “no hurry”.

“I said that at the right time you will come over, and we have a ways to go yet so we will see.”

Earlier, South Korea President Moon Jae-in had confirmed a meeting would take place.

“The leaders of the US and North Korea will have a handshake for peace standing at Panmunjom, the symbol of division,” Moon said, referring to the “truce village” in the DMZ.

“We’re going to the DMZ border and I’ll be meeting with Chairman Kim. I look forward to it very much. We’ve developed a very good relationship,” Trump said, hailing a “certain chemistry” between the two leaders.

But he was “in no rush” when it came to tensions on the Korean peninsula, Trump said, and stressed the meeting would be short.

“Just shake hands quickly and say hello because we haven’t seen each other since Vietnam,” he said, referring to a summit that collapsed without an agreement in February.

“It’s just a step and probably a step in the right direction,” said Trump.

South Korean people watch a broadcast of South Korean President Moon Jae-in and US President Donald Trump’s visit to the Demilitarised Zone.

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President Trump had extended an invitation to Kim on Saturday to coincide with his visit to South Korea after the G20 summit in Osaka. 

“Let’s see what happens,” the US President told business leaders in Seoul. “We are trying to work it out. It will be very short but that’s OK. A handshake means a lot.”

Their first meeting last year took place in a blaze of publicity, the first-ever encounter between a leader of the nuclear-armed North and a sitting US president, whose forces and their allies fought each other to a stalemate in the 1950-53 Korean War.

South Korean President Moon Jae-in (R) and US President Donald Trump speak during their talks at the presidential office Cheong Wa Dae in Seoul.

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That summit produced a vaguely-worded pledge about denuclearisation, but a second meeting in Vietnam in February intended to put flesh on those bones broke up without agreement. 

Contact between the two sides has since been minimal – with Pyongyang issuing frequent criticisms of the US position – but the two leaders have exchanged a series of letters.

“If Chairman Kim of North Korea sees this, I would meet him at the Border/DMZ just to shake his hand and say Hello(?)!,” Trump tweeted on Saturday from Osaka in Japan, where he was attending a G20 summit before flying to Seoul.