Donald Trump says US will defend allies from North Korea with 'full range of unmatched military capability'

'It's time to act with urgency and great determination,' says US President

President Donald Trump gestures during a joint press conference with South Korea's President Moon Jae-in at the presidential Blue House in Seoul (AFP/Getty Images)

Donald Trump has said the US will defend its allies against North Korea using the “full range of our unmatched military capabilities, if need be”.

The US President raised the spectre of nuclear war during a visit to Seoul, South Korea.

At a press conference alongside President Moon Jae-in, Mr Trump said Pyongyang’s nuclear and missile programmes were threatening “millions” of people.

“It’s time to act with urgency and great determination,” he said.

While the US was trying to talk Kim Jong-un down from his nuclear ambitions using “all available tools short of military action”, Mr Trump said that “the US stands prepared to defend itself and its allies using the full range of our unmatched military capabilities, if need be”.

He made similar comments earlier in his tour of the Asia-Pacific region, when he told troops at Yokota air base near Tokyo: “Together with our allies, America’s warriors are prepared to defend our nation using the full range of our unmatched capabilities.”

But Mr Trump added: “It makes sense for North Korea to come to the table and make a deal that is good for the people of North Korea and for the world.”

He said he had seen “a lot of progress” in dealing with Pyongyang and that he believed “ultimately, it’ll all work out”, adding a notably more upbeat line to his usual strong rhetoric.

Mr Moon said he and Mr Trump had finalised an earlier agreement to allow South Korea to possess more powerful missiles in the face of growing North Korean threats.

He said the two had agreed to lift the warhead payload limits on South Korean ballistic missiles and that the allies are also cooperating on strengthening South Korea’s defence capabilities through the acquisition or development of advanced weapons systems.

The US had three aircraft carrier strike groups in the western Pacific as Mr Trump left for his trip, a significant show of strength in a time of heightened tension.

At the press conference Mr Trump also called on every country to sever trade ties with North Korea “entirely”, naming Russia and China in particular. Repeated rounds of sanctions following Pyongyang's weapons tests have clamped down on its imports and exports.

South Korea is the second stop on Mr Trump’s Asia tour, which he is using to both shore up relationships with key allies and to push for new, “reciprocal” trade deals.

In Seoul he said a five-year-old trade agreement would be reassessed and that he hoped to “quickly pursue a much better deal”.

The current one has been “quite unsuccessful and not very good for the United States,” he added.

“Fair” trade was a key plank of Mr Trump’s “America First” campaign. He has long complained of deals he said have disadvantaged the US, and one of his first actions in office was to pull out of the Trans-Pacific Partnership, a multilateral agreement.

Hundreds of protesters demonstrated near the US embassy as Mr Trump made his visit. One band held signs reading “No Trump” and “No War”, and criticised the President’s attempt to re-write the trade deal.

Another group across the road chanted “USA!” as Mr Trump’s motorcade passed by and held signs that said “Blood Allies Korea + US”.