The North Korean regime is guilty of "paranoid rhetoric" after warning last week that it could not guarantee the safety of embassy staff in the event of a war, William Hague has said.

As the US moved to ease tensions by postponing a missile test in California, the foreign secretary urged Britain and other allies to remain calm as he said there were no signs of a major military buildup.

Speaking on the BBC's Andrew Marr Show, Hague said: "We have to be concerned about the danger of miscalculation by the North Korean regime, which has worked itself up into this frenetic state of rhetoric in recent weeks, and the danger that they would believe their own paranoid rhetoric. But it is important that the international response to this, including our response, must be clear and united and calm."

The foreign secretary declined to comment on British and other intelligence about the military threat from North Korea. But he indicated that intelligence suggested Pyongyang did not pose a major threat when he said there were no signs of the sort of military buildup that would be expected before a major conflict.

"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 have not 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. That is why I say it is important to keep calm as well as to be firm and united about this."

The foreign secretary's remarks came after Chuck Hagel, the US defence secretary, postponed the test launch of a Minuteman 3 intercontinental missile from a California airbase until next month in an attempt to reduce tensions.

Hague said the behaviour of the regime of North Korea's leader, Kim Jong-un, was typical of authoritarian leaders who needed to shore up their position by creating an external threat. "What is going on here could easily be what we have often seen throughout history among authoritarian and totalitarian regimes. Remember that this is a regime that has to justify the intense militarisation of their society and the development of these weapons and missiles, even though many people in their country are regularly and seriously short even of food.

"To justify that you have to have an external threat … or danger you can point to. I think the announcement last week that foreign embassies could not necessarily be protected after Wednesday of next week, which is what they said to our embassy, is also consistent with that.

"But I haven't seen any immediate need to respond to that by moving our diplomats out of there. We will keep this under review with our allies. But we shouldn't respond and play to their rhetoric and that presentation of an external threat every time they come out with it."

Hague drew a contrast between the pre-industrial revolution state of the North Korean countryside and the regime's development of missiles. "There is an enormous gap. This is a country where many people are working in the field. It is a case of manual labour in the fields without many tractors – so they are short of tractors. But they do have the machines that carry long-range and intermediate-range missiles around.

"If the leadership of North Korea continue on their current path over the coming months and years, they will end up leading a broken country that is internationally isolated."