Despite North Korea announcing it has successfully launched an intercontinental ballistic missile, South Koreans consider Donald Trump to be a bigger threat to their security than Kim Jong-un, according to former foreign affairs minister Gareth Evans.

"Kim Jong-un's behaviour is often rather idiosyncratic, it's also often very ugly but I don't think anybody thinks he's nuts," he told 7.30.

"It's very clear that South Koreans are more worried about Donald Trump than they are about the North Koreans in terms of what might trigger an actual conflict in which they'd be caught up and devastated."

While he believes a deliberate nuclear strike by either the US or North Korea is unlikely, Mr Evans said he was worried about how the US President may respond to future provocations.

Sorry, this video has expired You've got to be concerned about a nuclear miscalculation with the North Korean situation

"What you've got to be concerned about is not so much a deliberate, offensive strike but rather a misjudgement about a provocative situation, a retaliation that goes too fast that doesn't take into account possibilities for diplomatic soothing of a situation, just a reflex emotional response to a provocation," he said.

"We just can't assume with this President that if there are any adults around him they will in fact prevail in this situation."

Sheer dumb luck we've avoided a nuclear holocaust

Sorry, this video has expired Sheer dumb luck there's not been a nuclear holocaust

Despite fears the missile recently fired by North Korea could reach the US and Australia, Mr Evans argued the bigger threat was a nuclear accident.

"It's sheer, dumb luck that we've managed to avoid a nuclear weapons holocaust for the last 75 years," he said.

"It's not because of anything inherently stable about the deterrent system, it's not because of any inherent brilliance of the statesmanship of those with their fingers on these triggers, it's sheer, dumb luck."

"And I worry of course that so long as anyone retains nuclear weapons, certainly someone like North Korea, there is this risk."

Warning we shouldn't be "spooked" by recent developments, Mr Evans said containment, deterrence and open negotiations were the best option for pulling North Korea into line.

"There's no guarantee that approach would achieve any time soon the de-militarisation of the peninsula. But there's a reasonable chance it could deliver a freeze," he said.

"It's the only game in town."