While analysts do not expect an actual strike by North Korea, which could trigger a suicidal war, a series of intense threats continue to be issued by the country.
"The highly unpredictable and aggressive regime in North Korea recently conducted its third nuclear test and could already have enough fissile material to produce more than a dozen nuclear weapons," David Cameron said, writing for the Daily Telegraph.
"Last year, North Korea unveiled a long-range ballistic missile which it claims can reach the whole of the United States."
If this became a reality, it would also affect the whole of Europe - including the UK.
Prime Minister David Cameron
A spokesman for the Korean People's Army has formally informed the White House and Pentagon that the "ever-escalating hostile policy and reckless nuclear threat" of the US would be "smashed".
The statement added that "cutting-edge smaller, lighter and diversified nuclear strike means" would be used.
According to South Korea, their neighbours have moved a missile with "considerable range" to the east coast - but Defence Minister Kim Kwan-jin dismissed reports that the missile could be a KN-08.
That type of long-range missile, if operable, could hit the US.
The Pentagon has taken the decision to deploy a missile defence system to the US Pacific territory of Guam to strengthen protection against a possible strike.
US Defence Secretary Chuck Hagel says Washington is doing all it can to defuse the situation.
"Some of the actions they've taken over the last few weeks present a real and clear danger and threat to the interests, certainly of our allies, starting with South Korea and Japan," he said.
The US had better ponder over the prevailing grave situation.
Korean People's Army
Meanwhile, Mr Cameron insists that while the world has changed dramatically, the need for the UK's nuclear deterrent remains.
"The Soviet Union no longer exists. But the nuclear threat has not gone away," he said.
"In terms of uncertainty and potential risk it has, if anything, increased."
The prime minister also expressed concerns over Iran continuing to defy the will of the international community over its nuclear programme.
"Does anyone seriously argue that it would be wise for Britain, faced with this evolving threat today, to surrender our deterrent?" Mr Cameron said.
"Only the retention of our independent deterrent makes clear to any adversary that the devastating cost of an attack on the UK or its allies will always be far greater than anything it might hope to gain."
The Conservatives are committed to replacing the ageing Trident submarine fleet with like-for-like models, but their Liberal Democrat coalition partners are seeking a cheaper alternative.
Labour say retention of an independent nuclear deterrent is "absolutely right", but that the costs involved must be taken into account.
The future of Trident is likely to feature in next year's Scottish independence referendum campaign, with the SNP insisting it would not allow nuclear missiles to be based in an independent Scotland.