Buried deep beneath the Montana soil in America's northwest are 150 giant Minuteman III nuclear missiles - locked, loaded and ready to go.

They are 20 times more powerful than the atomic bomb dropped on Hiroshima and can reach any target on the planet in half an hour.

They stand ready to be deployed at any moment of the day, on the order of US President Donald Trump, who this month promised North Korea a "fire and fury like the world has never seen".

A Minuteman III missile flaming into the sky from Vandenberg Air Force Base, Lompoc, California. Photo / AP
A Minuteman III missile flaming into the sky from Vandenberg Air Force Base, Lompoc, California. Photo / AP

"I think this is a very dangerous time - perhaps the most dangerous threat that we've faced since the Cuban missile crisis," former US Secretary of Defence Leon Panetta said.

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Tensions between America and North Korea have been simmering for months, reaching a frightening war of words in recent weeks.

The two countries have exchanged threats and counter threats over recent weeks, with the world watching nervously.

And should they boil over, it's from this location that Trump's "fire and fury" will be unleashed.

Channel Nine's 60 Minutes programme received a rare look at the nuclear facility in Montana, which is just part of the mega arsenal that serves as a deterrent.

There are countless others just like it, with some 450 "super nukes" in stockpile.

It's a never-ending operation to be ready, with constant training on how to maintain and handle the weapons.

Master sergeant Jennifer Hubner said should the call from the White House come, she and her colleagues were ready.

"None of us come to work hoping today's the day. But we hope our enemies think twice before they decide to use weapons of mass destruction against us or our allies."

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A man in Seoul, South Korea watches a television screen showing US President Donald Trump and North Korean leader Kim Jong-un. Photo / AP
A man in Seoul, South Korea watches a television screen showing US President Donald Trump and North Korean leader Kim Jong-un. Photo / AP

That includes Australia, with Hubner declaring: "We've got your back".

Reporter Liz Hayes was granted unprecedented access to a control room 20 metres underground, where the launch of the world's most devastating weapons would occur.

At the panel are two "missileers", inside a small concrete and steel room suspended by shock absorbers designed to withstand a nuclear blast.

"And it's always manned, with 'missileers' rotated on 24-hour shifts," Hayes explained.

The US will splash US$340 billion on nuclear weapons in the next decade to maintain its global "deterrent" against enemies like North Korea.

North Korea won't back down on its global threats and US President Donald Trump is also standing firm, resulting in a dangerous stand-off. Photo / AP
North Korea won't back down on its global threats and US President Donald Trump is also standing firm, resulting in a dangerous stand-off. Photo / AP

"No enemy can escape our missiles. None. We have the capability to hold any enemy on the planet accountable," Commander Ronald Allen said.

North Korea's dictator Kim Jong-un has ramped up his threats to attack the US but Panetta warned Australia was also at risk.

He believes the Federal Government should consider building its own nuclear weapons chest.

"You have to protect your country," he said.

A look at the MInuteman III missile. Photo / 60 Minutes
A look at the MInuteman III missile. Photo / 60 Minutes

"There could come a moment in time that [Kim] could also have to face it may be the end of his regime, when he decides that pushing the button [will mean] history will remember him."

What happens should nuclear war occur is a total unknown, he said.

It would almost certainly result in hundreds of thousands, if not millions of deaths, with devastation on an unprecedented scale.

"And how does that play out in the rest of the world? We're not sure how it comes to an end."

He predicted the next few months were going to signal the direction the world would take.

Declassified film of American nuclear bomb testing has just emerged after years lying in a vault

By News Corp Australia Network staff writer