Trump urges all nations to isolate North Korea's 'cruel dictatorship'

US President Donald Trump on Wednesday called for isolation of North Korea - what he calls a cruel dictatorship- by all nations including Russia and China during his speech in South Korea's National Assembly in Seoul.

He urged countries around the world to join together to isolate Pyongyang by denying it "any form of support, supply or acceptance."

"The world cannot tolerate the menace of a rogue regime that threatens it with nuclear devastation," Trump said.

He warned North Korea not to "underestimate us and do not try us."

The US president said that, "We will not allow American cities to be threatened with destruction. We will not be intimidated, and we will not let the worst atrocities in history be repeated here, on this ground we fought and died to secure." 

"America does not seek conflict or confrontation, but we will never run from it," he added. "We will not permit America or our allies to be blackmailed or attacked."

Trump offered North Korean leader Kim Jong-Un what he called "a path towards a much better future."

The US president also told North Korean leader Kim Jong Un that the nuclear weapons and ballistic missiles he's acquiring "are not making you safer" but "are putting your regime in great danger."

"Yet despite every crime you have committed against god and man," he went on, "we will offer a path towards a much better future".

Secret visit cancelled

Trump also abandoned a surprise visit to the Demilitarized Zone that divides the two Koreas on Wednesday because of bad weather, leaving him "pretty frustrated" according to the White House.

South Korean leader Moon Jae-In, who had flown earlier before the weather closed in, was left waiting at a guard post on the border, which bristles with electric fences, minefields and anti-tank barriers.

The US chief executive, who the White House had previously said would not go to the symbolic spot, took off from the Yongsan military base in Seoul, but his helicopter then had to turn back due to fog.

Visiting US presidents have regularly gone to the DMZ, where soldiers from North and South Korea face off along a border marked by concrete blocks between blue huts. 

Administration officials had said before Trump's Asia tour that he would not make the trip, saying it was "becoming a little bit of a cliche, frankly" after visits by Vice-President Mike Pence and Defense Secretary Jim Mattis.

But Trump said at a state dinner Tuesday evening: "We are going to have an exciting day tomorrow for many reasons that people will find out," without elaborating.

Reporters accompanying him were summoned earlier than scheduled Wednesday and press secretary Sarah Huckabee Sanders told them: "This is where we're going," holding up a piece of notepaper on which the letters "DMZ" were scrawled.

Trump's helicopter Marine One took off from Yongsan, but was forced to turn back, only about five minutes from landing. The group waited nearly an hour for conditions to improve, but the weather worsened instead and the trip was abandoned. 

"He's actually pretty frustrated," said Sanders. "There wasn’t enough visibility to land. It would have been really dangerous, and our guys pulled back."

It would have been a "historic moment" as the first time US and South Korean presidents had visited together, she said.

"It still, I think, shows the strength of the alliance and the importance of it that they were going to do this," she added.