William Hague has called for calm over tensions in the Korean peninsula but added Britain "should be concerned" about North Korea's activities.
The Foreign Secretary said the "danger of misclaculation" by Kim Jong Un's regime, which had worked itself up into a "frenetic state of rhetoric", must be considered.
He stressed there were no signs that North Korea was beginning to re-position its forces ready for war.
Speaking on BBC 1's Andrew Marr Show on Sunday, he said: "There's a threat to the world from any country breaching the non proliferation treaty, which North Korea is doing, acting in contravention of a whole series of UN Security Council resolutions and setting out to develop more and more longer range weapons, testing new nuclear weapons and indulging in the proliferation of many items to other countries as well.
"We should be concerned about that. There is a danger in that.
"But it is important to stress that we haven't seen in recent days, in recent weeks, a change in what is happening in North Korean society. We have not been able to observe that. We've haven't seen the repositioning of forces or the redeployment of ground forces that one might see in a period prior to a military assault or to an all out conflict."
Hague declined to speculate on whether the 29-year-old dictator was "nuts".
He said: "I don't know the man myself of course. It's not easy, although we have an embassy there, it's not easy to get face to face discussions with North Korean leaders so I'm not going to speculate about the psychology of the leader of North Korea except in the terms that I have already spoken about - that authoritarian and totalitarian regimes perfectly rationally from the point of view of their own survival in the short term often do this sort of thing, try to ramp up an external threat."
It comes after North Korea announced on Friday that it will not guarantee the safety of international embassies in Pyongyang if war breaks out.
The Foreign Office has said it has "no immediate plans to withdraw'' Britain's embassy in Pyongyang and condemned the "provocations'" of the North Korean regime.
The United States announced on Sunday it had cancelled a planned test of a Minuteman 3 intercontinental ballistic missile (ICBM) over fears of escalating tensions on the Korean peninsula.
The test, which was due to take place next week from the Vandenberg Air Force Base in California, has been delayed for a month following a series of increasingly bellicose threats from Pyongyang.
Hague told Murnaghan on Sky News the regime claimed to have weapons that could hit the United States and echoed prime minister David Cameron's claim that the situation backed the case for a Trident successor.
"If they did so, well, then most of Europe and the United Kingdom would be within range as well so it is an illustration of how it is very important, in the future decades, to keep our own ultimate line of defence and to have a successor to the Trident submarines."
North Korea was targeted by hacker groups last week who took control of the central news agency Uriminzokkiri's website, Twitter account and Flickr page.