North Korea has marched straight up to Trump's red line

The pace of the developments is so rapid that North Korea is already close to calling Mr Trump’s bluff - and his options are limited

A file photo distributed by the North Korean government last month shows what was said to be the launch of a Hwasong-14 intercontinental ballistic missile

Donald Trump’s promise of “fire and fury” raining down on North Korea was not part of unscripted outburst.

Reporters at his New Jersey golf club said he appeared to glance down at a piece of paper as he made his remarks.

Yet quite what he meant by them remains to be seen.

For while his remarks echoed Harry Truman’s announcement that the US had dropped an atomic bomb on Hiroshima in 1945 – which he described as "a rain of ruin from the air, the like of which has never been seen on this earth” – they came without the sort of talking points or briefings to explain what comes next.

The danger, as John McCain, the Republican senator, spelled out, is that such blunt rhetoric without action ends up sounding hollow.

"I take exception to the president’s comments because you got to be sure you can do what you say you’re going to do,”€ he said in a radio interview.

The problem for Mr Trump is that North Korea has marched straight up to red line he set in January when he said he was not going to let Pyongyang develop a nuclear weapon that could threaten the US.

Since then, Kim Jung-un’s regime has built inter-continental ballistic missiles (ICBM) with a theoretical range that brings the American mainland within reach.

And then this week, the Washington Post reported that military analysts believe his engineers have miniaturised nuclear devices so they could be carried by an ICBM.

That still leaves the matter of developing re-entry and targeting systems, but the pace is so rapid that North Korea is already close to calling Mr Trump’s bluff.

His options are limited.

The United Nations imposed yet more sanctions on the hermit state at the weekend. But more than a decade of embargoes have apparently yet to slow the progress of North Korea’s nuclear weapons programme.

China, which has the economic clout to make sanctions bite, has so far been reluctant to completely choke off support, much to Mr Trump’s frustration.

Military options are also limited. While the Pentagon has a slew of plans for toppling the regime or taking out its nuclear launch sites, Pyongyang’s conventional weapons would almost certainly rain their own retaliatory fire and fury down on American bases in South Korea and on civilians in Seoul.

Even bolstering defences against North Korea runs the risk of accidental confrontation or escalating the existing arms race.

That leaves negotiating with a government that many Americans view as evil or crazy.

A day before Mr Trump’s comments, Rex Tillerson, the US Secretary of State, laid out the possible pre-conditions for talks, quietly dropping previous insistence that nuclear testing stop and focussing instead on the ICBM tests.

“The best signal that North Korea could give us that they’re prepared to talk would be to stop these missile launches,” he said.

Although he has offered softer rhetoric than Mr Trump, insisting for example that the US is not seeking regime change, the end point of any negotiations remains a nuclear-free Korean peninsula.

That remains unacceptable for a dictatorship which believes nuclear weapons are essentially for its survival. In the past it has cited the examples of Saddam Hussein and Muammar Gaddafi as case studies in leaders who give up nascent nuclear weapons programmes.

In the absence of obvious options and with little sign of a plan the danger is that Mr Trump’s rhetoric may only have one, unintended consequence: Pushing North Korea towards even more desperate measures.

As Bruce Klinger, a former CIA analyst who is now senior research fellow at the conservative Heritage Foundation, put it: “President Trump’s comments sound as if they were penned by Pyongyang. His statement is unhelpful and will affirm growing perceptions that the US is considering a preventative military attack against North Korea.”