BY any standards it is a tantalising prospect. The news that Donald Trump, President of the United States, is to meet North Korean leader Kim Jong Un within weeks has left a few diplomatic jaws dropping in near disbelief.

After all, it was only recently that Mr Trump threatened to rain “fire and fury” down on North Korea while Mr Kim, in his characteristically surreal response, insisted he would “tame the mentally deranged US dotard with fire.” It was angry, belligerent talk that at times had the world contemplating the possibility of a catastrophic, all-out war between the two nations.

Suddenly, marking a turnaround in communications, there is the chance of the first summit between the US and North Korea after Pyongyang offered to suspend its nuclear and missile tests.

Both countries have been here before, albeit not for some time. Diplomacy between America and North Korea has gone through cycles of long stagnation, followed by brief bursts of hope and then disappointment, typically after North Korea reneged on any agreement.

Though there have been repeated attempts to denuclearise North Korea , the fact that no sitting US president has ever met a North Korean leader speaks volumes about the significance of the forthcoming meeting and the considerable challenges that lie ahead. Mr Trump and his administration are acutely aware of this and face a prospect not unlike that confronted by Bill Clinton, George W. Bush and Barack Obama; in other words, being dragged down the same complex, unpredictable, sometimes illusory and often inconclusive diplomatic path as their predecessors.

They must know, too, that, to a great extent, Mr Kim will more than likely simply reuse the playbook used by his father, Kim Jong-il, and grandfather, Kim Il-sung. In a move one former US official described as “vanity over strategy”, many security advisers have cautioned against a meeting they see as giving a degree of credibility to Mr Kim.

It allows North Korea to be recognised as a de facto nuclear state and gives Mr Kim a seat at the diplomatic table without having made any concessions, they argue. In response, South Korean officials insist they have already extracted a number of concessions from the North, among them agreement that routine large-scale joint military exercises between South Korean and America will go ahead.

These manoeuvres had already been delayed because of the Winter Olympics and who can forget that it was there, in great part, that this process of rapprochement first became public, encouraged by South Korea’s president, Moon Jae-in? This was not all to Washington’s liking, of course, as evidenced when US vice-president Mike Pence went out of his way to snub North Korea’s ceremonial head of state Kim Yong-nam at an opening ceremony dinner in full view of his South Korean hosts.

It is understandable that the US is wary of a North Korean offer of talks that might simply be an attempt to shove a wedge between Washington and its crucial alliance with South Korea or a ruse in playing for time over Pyongyang’s nuclear weapons programme.

It is important also to consider that Moon Jae In, the South Korean leader, was elected on a promise of closer relations with the North and would be only too willing to embrace any potential opportunity to consolidate that position. Then there is the intriguing possibility that Pyongyang maybe sending a new kind of signal; that, in fact, Mr Kim is genuinely keen on dialogue, perhaps because international sanctions on the North may have hurt his country’s economy to the point that he feels compelled to talk. Regardless of the motives on all sides, the fact that talks have been broached is to be welcomed.