DONALD Trump warned the US is poised to unleash the full force of its military power to defend against the "worldwide threat" from North Korea.

The US President took a tough stance during his visit to South Korea today, saying tyrant Kim Jong-un is threatening "millions" of lives.

20 Donald Trump warned the US is poised to unleash the full force of its military power to defend against North Korea Credit: Getty Images - Getty

He called on world powers, particularly China and Russia, to act with "urgency and great determination" to put more pressure on the North.

"We cannot allow North Korea to threaten all that we have built," Trump told the press conference on the first day of his visit on Kim’s doorstep.

"North Korea is a worldwide threat that requires a worldwide action.”

Trump made it clear that the US was fully prepared to wield the “full range” of America’s arsenal, but added: "We hope to God we don't have to”.

20 Standing alongside his South Korean counterpart Moon Jae-in, the US President urged the North to take part in talks Credit: EPA

20 The US President took a tough stance during his visit to South Korea today Credit: AP:Associated Press

20 He called on world powers, particularly China and Russia, to act with "urgency and great determination" Credit: AFP or licensors

President Donald Trump deliver​s​ a speech to South Korea's national assembly

He said: "As we work together to resolve this problem using all available tools short of military action, US stands prepared to defend itself and its allies using the full range of our unmatched military capabilities if need be.”

Standing alongside his South Korean counterpart Moon Jae-in, the US President urged the North to take part in talks.

But Trump declined to elaborate on whether US is having any direct talks with its regime.

"I really believe it makes sense for North Korea to come to the table and to make a deal that is good for the people of North Korea and the people of the world," he said.

20 Trump began his diplomatic day vowing to "figure it all out" with "fine gentleman" Moon Credit: AP:Associated Press

20 Trump's relationship with the liberal-leaning Moon has been cool in the past Credit: EPA

He insisted they are “making a lot of progress” in reining in the rogue state.

Trump's relationship with the liberal-leaning Moon has been cool, and the billionaire has railed at South Korean moves to engage its neighbour - something he has previously labelled "appeasement".

How big is North Korea's army and what missiles does Kim Jong-un have?

But Trump began his diplomatic day vowing to "figure it all out" with "fine gentleman" Moon, despite their differences on the nuclear-armed North.

He landed in South Korea on Tuesday, bringing him to the frontline of the nuclear stand-off with North Korea.

The US President waved to the crowds when he arrived at Osan Air Base outside Seoul today as despot Kim Jong-un vowed to “bolster its nuclear sword of justice”.

20 Donald Trump waved to the crowds when he arrived at Osan Air Base in South Korea with his wife Melania today Credit: Reuters

20 Melania Trump wore a striking outfit for the occasion Credit: AFP or licensors

20 The First Couple were seen sharing a slightly awkward kiss on the red carpet Credit: AP:Associated Press

20 Trump's 24-hour visit right on Kim’s doorstep is likely to aggravate tensions with North Korea Credit: AP:Associated Press

His 48-hour visit right on Kim’s doorstep is likely to aggravate tensions with North Korea, especially after boasting he could stop the tyrant’s nukes during his visit to Japan.

South Korean President Moon Jae-in welcomed Trump and his wife Melania at Camp Humphreys, America's biggest military base in the Pacific.

The surprise move was intended to show the robust alliance amid North Korea’s persistent nuclear threats.

Trump said efforts to stop North Korea's nuclear weapons program would be "front and centre" of his two-day visit to South Korea.

20 He shook hands with South Korea’s President Moon Jae-in during a visit to the presidential Blue House in Seoul Credit: Reuters

20 Trump looked a little tense as he stood next to the South Korean leader during the visit Credit: AFP or licensors

20 Trump said efforts to stop North Korea's nuclear weapons program would be 'front and centre' of his two-day visit to South Korea Credit: AFP or licensors

20 The First Couple received a formal welcome at the presidential Blue House, just 35 miles from the border with North Korea Credit: AFP or licensors

Meeting with military commanders, Trump told reporters: “Ultimately it will all work out, it always works out, it has to work out”.

Trump later received a formal welcome at the presidential Blue House, just 35 miles from the border with North Korea.

Moon said he hoped Trump's visit would be an opportunity to resolve "anxiety" over North Korea.

"I know that you have put this issue at the top of your security agenda," Moon said.

"So I hope that your visit to Korea and to the Asia Pacific region will serve as an opportunity to relieve some of the anxiety that the Korean people have due to North Korea's provocations and also serve as a turning point in resolving the North Korean nuclear issue."

Trump praised president Moon, hailing him for “great cooperation,” despite differences over how to confront North Korea and over a trade pact between the US and South Korea.

The US President said he looked forward to a "successful day of talks."

The White House says Trump’s trip is intended to demonstrate US resolve over his hardline approach to the North Korean nuclear and missile threats.

But many in the region fear more fiery presidential rhetoric could increase the potential for a devastating military conflict on the Korean peninsula.

Pyongyang’s recent nuclear tests in defiance of UN resolutions have raised the stakes in the most critical international challenge of Trump’s presidency.

20 Trump posed with generals and other military officials at the Army Operational Command Centre at Camp Humphreys in Pyeongtaek Credit: AFP or licensors

20 He was photographed shaking hands with military commanders Credit: AFP or licensors

20 Moon said he hoped Trump's visit would be an opportunity to resolve anxiety over North Korea Credit: EPA

Trump is seeking to ratchet up pressure on Pyongyang following his time in Tokyo.

During the visit he declared that Japan would shoot North Korean missiles “out of the sky” if it bought the US weaponry needed to do so.

This suggested the Japanese government may take a stance it has avoided until now.

In Japan, Trump refused to rule out eventual military action against the North and called on Kim to stop weapons testing.

He branded the recent launches of missiles over American allies like Japan "a threat to the civilized world and international peace and stability."

Three US aircraft carrier strike groups will exercise together in the Western Pacific in the coming days in a show of force rarely seen in the region, US officials said.

20 Trump saluted as he got out of helicopter at Camp Humphreys Credit: EPA

20 Trump greeted General Jeong Kyeong-doo, chairman of South Korea's Joint Chiefs of Staff, after arriving at Camp Humphreys Credit: EPA

South Korea is the second stop on Trump's five country Asian tour.

Trump is skipping the customary trip to the demilitarized zone separating North and South a pilgrimage made by every US president except one since Ronald Reagan as a demonstration of solidarity with the South.

A senior administration recently dubbed the border trip as "a bit of a cliche" and several other members of the administration, including Vice President Mike Pence, have visited the DMZ this year.

It is feared that North Korea could launch the huge hydrogen bomb dubbed the 'Juche Bird' over the Pacific Ocean during the visit, the Daily Star reported.

Such an unprecedented test, the kind of which hasn’t been seen in three decades, could spark a global nuclear conflict.

The White House believes that Trump has already made his support of South Korea crystal clear.

20 Melania was seen speaking to middle school students during the Girls Play 2! initiative Credit: Reuters

NORTH SOUTH DIVIDE History of conflict between North and South Korea North and South Korea have been in a state of war for more than half a century and the hostility between the two countries shows no sign of abating. Until after the Second World War, Korea was a unified country and was the object of desire from both China and Japan, with Japan claiming the territory in 1910. Japan remained in control of Korea, suppressing its culture and imposing its own despite much opposition until the end of World War II. In the closing days of the war with the axis facing defeat, Russia declared war on Japan and marched into Korea. However, with tensions also rising between Russia and the West, America didn’t want Russia to have complete control over Korea. It was therefore agreed that Russian forces would stop at the 38th parallel north, leaving the south of the country, including its capital Seoul, to America. It was originally intended that Russian and American cooperation would steer Korea towards independence. But as their relationship deteriorated, both nations asserted their authority. North Korea adopted the socialism of Soviet Russia, becoming the Democratic People’s Republic of Korea, while the South became the Republic of Korea, implementing a more Western style of government. Both Russia and the US appointed leaders in their respective territories who would implement their policies, with the anti-Communist Syngman Rhee in the South, and Kim Il-Sung in the North, the father of Kim Jong-Il. This was the start of the hostility, as both governments believed themselves to be the government of all Korea, resulting in frequent clashes along the border. This led to the outbreak of war in 1950 when the North invaded the South and quickly overran the country, thanks to its use of Soviet tanks and weaponry. The UN, led by America, quickly intervened and helped the South push back North Korean forces. They retreated to the Chinese border, which then provoked China to intervene on behalf of North Korea, shifting the balance again. The war ended in 1953 with no clear victor and an armistice was signed between the North and South to restore the previous boundaries. However, much of Korea was destroyed with over a million casualties and Seoul in ruins after having changed hands four times over the course of the war. Following the demise of the Soviet Union, the North was plunged into an economic crisis and suffered a catastrophic famine.