DO NOT expect much good to come of Donald Trump’s impulsive, off-the-cuff decision to accept an invitation to meet North Korea’s dictator, Kim Jong Un, “by May”. For such a summit to maximise its chances of success would have required careful and painstaking back-channel diplomacy of the kind exemplified by Henry Kissinger before Richard Nixon made his historic visit to China in 1972. Mr Trump should have waited for the results of exploratory negotiations before rushing in.

One reason for his impatience is his contempt for such traditional diplomacy. It does not appear to bother him that he has yet to appoint an ambassador to Seoul, the capital of South Korea, or that the wretchedly depleted State Department has just lost its main expert on North Korea, Joseph Yun. Mr Trump no doubt believes that it is his toughness alone that has brought Mr Kim to the negotiating table and that, once there, his unique force of personality and his genius for the deal will bully and coax Mr Kim into giving up his nukes.

In fact hell will freeze over before Mr Kim voluntarily surrenders a capability that his father and grandfather believed would be the ultimate guarantor of their dynasty’s survival and which has taken decades and huge sacrifices to construct.

Tightening sanctions and loose talk in Washington of a bloody-nose strike on his nuclear facilities may indeed have persuaded Mr Kim that this was a good moment to strike up a dialogue. But he will also believe that it is only because he is very close to having nuclear-armed missiles which can hit the United States that Mr Trump is so keen to meet him.

In other words, it is his nukes that demand respect. They have created the conditions for him to be treated by an American president as an equal rather than as an awkward pariah.

Mr Kim’s apparent offer to discuss denuclearisation of the Korean peninsula in exchange for what South Korean officials have described as “security guarantees” looks like little more than a cynical ruse. He knows well that the guarantees he wants cannot be offered. But he may still get something in return for a (probably short-term) moratorium on missile testing. He may be calculating that this will include an easing of tension and an excuse for China and Russia to throttle back on sanctions.

By engineering a meeting with Mr Trump, Mr Kim will also win an incalculable boost to his own prestige at home. It will demonstrate to his benighted people that his power is not to be challenged and that his nuclear weapons have given North Korea status and influence. Mr Trump has given away the prize of a summit without getting anything in return except the shock-value of wrong-footing expectations at home and around the world, including, most likely, in North Korea.

Mr Trump’s meeting the despot formally known as “little rocket man” will not necessarily be a total flop. If the two get on well personally, which is by no means impossible, it could just pave the way for more substantive negotiations—though, even then, expectations should be set low.

The risk, however, is that an inadequately prepared summit between these leaders will fall into one of two traps. The first is that Mr Kim succeeds in charming the impetuous and inexperienced Mr Trump to such an extent that he makes foolish concessions that his opposite number has no intention of earning. The second is that, if it dawns on Mr Trump that he has been played by Mr Kim and made to look naive, he may react like a jilted, misled suitor. The motto for talks with North Korea should be “proceed with caution”. A premature summit, by contrast, is an ill-considered roll of the dice.