After a two-month pause, North Korea launched its most advanced ever missile this week, warning it is now capable of striking anywhere in the world.
That has led to calls from hawks in the US for military action against Kim Jong-un’s vile regime.
And Jim Hoare, the former British chargé d’affaires in Pyongyang, said Mr Trump appeared to have missed his chance to defuse the escalating conflict.
He said of the newest launch: “It’s certainly not surprising in one sense. They have a programme and they’re continuing with it and will do until they reach their goal.
“But on the other hand they’ve been quiet for a bit.
“I think they were waiting to see if being quiet produced any positive reaction.
“But it didn’t. What it produced instead was Mr Trump putting them back on the terror list.”
Mr Hoare, whose work in the region eventually led to the establishment of a full embassy in Pyongyang, is one of the few westerners to have seen the Kim dynasty’s reign up close.
And he warned Mr Trump’s constant mockery of the tyrant, most recently branding him a “sick puppy”, was only increasing the likelihood of conflict.
His previous belittling of the leader as a “rocket man” went against advice from officials who warned him not to make things personal and led to the North accusing the US of declaring war.
The President used the insult again this week, tweeting: “The Chinese Envoy, who just returned from North Korea, seems to have had no impact on Little Rocket Man. Hard to believe his people, and the military, put up with living in such horrible conditions.”
Mr Hoare said “flattery” could take the form of another visit from a key US official, the way diplomat Madeleine Albright did in 2000 under the Clinton administration.
He said: “Kim Jong-Il certainly reacted positively to engagement with the US and the visit of Madeleine Albright and so on.
“I’ve always thought that some form of more formal recognition, accepting he’s a powerful person, whether you think so or not, respect and flattery if you like, is perhaps the most important thing.
“All the things Trump does are not designed to do that.
“That’s not the right way to conduct international affairs.
“It may be Mr Trump’s way but I don’t think it’s the right way.
“If you want to influence an individual you don’t call them too many names, you don’t make fun of them.”
But many in the US are now saying that previous attempts to placate the regime have proved to be a failure.
And some think the crisis can only be solved by either accepting a nuclear armed North Korea or taking military action.
John Bolton, former US Ambassador to the UN, warned this week that the US would now have to follow up its hardline threats with action.
He told Sky News: “I don’t think it would be a major war, I think what the US has to look at is destroying North Korea’s ballistic missile facilities and its nuclear facilities.
“I think as well we would have to take step to protect against North Korean retaliations against South Korea and what they would probably do is attack the city of Seoul.”
He added: “The tough rhetoric that we’ve used, if its not followed by tough action, leaves us in a worse position.”