It is a relief that the June 12 US-North Korea summit in Singapore will -- at least for now -- be going ahead. The two sides are holding multiple working-level contacts to prepare the meeting. But it still is too early to predict that everything will run to plan, since unpredictability has become the norm of the rollercoaster summit.

One major cause of the “you-don’t-know-what-will-happen-tomorrow” situation is the frequent flip-flops on the part of the two main players -- Kim Jong-un and Donald Trump. The two men are apparently trying to take the upper hand in the upcoming talks, but their rashness, abruptness and injudiciousness, along with their strategic calculations, could -- as it showed last week -- jeopardize the denuclearization talks at any time.

The rollercoaster ride on the way to the summit is indeed mesmerizing. Kim offered peace to the South and asked President Moon Jae-in to broker a meeting with Trump. The US president, already well known for his quick, but often inconsiderate and injudicious decisions, accepted, but only to pull out for less than convincing reasons and revive it in a matter of a day.

Of course, Kim is primarily to blame for starting all the upheavals. Perhaps Kim, who knows what his grandfather and father did with former South Korean and US leaders, thought brinkmanship would work with Moon and Trump as well.

Kim’s first target was the South. It was even before the ink dried on the Panmunjeom Declaration he signed with Moon on April 27 that he canceled high-level talks with the South on May 16 -- sending a notification just 10 hours ahead of the planned time. The North allowed South Korean journalists to join a pool of international media to cover the dismantling of its nuclear test site in Punggye-ri only at the last minute. That’s typical of Kim’s tactics, emphasizing what his counterpart might lose.

As it turned out, the North’s about-turn against the South was a prelude toward resuming hostility against the US. That, of course, was aimed to strengthen its negotiating position. The offensive started by blasting National Security Adviser John Bolton for mentioning a Libyan-style denuclearization. Then a separate statement, which became famous for calling out Vice President Mike Pence a “political dummy,” went on to warn cancellation of the summit and “a nuclear showdown.”

All seasoned diplomats and security experts would know that the North was bluffing -- as Trump often does -- again resorting to its usual brinkmanship to strengthen its position. But Trump, in his usual single-handed manner, took it as a chance to initiate his own brinkmanship, pulling out of the talks where he had said too much is at stake.

In a sense, it is true Trump’s “maximum pressure” that means harshest-ever sanctions against the North and his “fire and fury” stance -- all augmented by his personality -- have succeeded in getting Kim to the negotiating table.

But at the same time, his about-turns -- for instance, he once called Kim a “little rocket man and madman,” and later an “honorable man” --have caused confusion over where he and Kim were headed.

He also manifested his usual egoistic and disrespectful attitude when he canceled the meeting. He even did not consult or inform Moon, who brokered the meeting and whom he had met only a few days ago in Washington.

After North Korea issued what he called “warm and productive statement,” Trump, when questioned by reporters if North Korea was playing games, Trump said that “everybody plays games.”

True, every diplomatic negotiation is a game. What both Trump and Kim should realize is that the game they are playing now is about a nuclear crisis and is too important to be swayed by their usual thinking and behavior, not least lack of restraint and rashness. We don’t expect the two men to behave as statesmen, but they could at least be a little more sensible.