No matter where negotiations take place, the give and take of the two sides has some time-honoured tenets.

One is to understand your adversary's true aim in negotiations, and to make sure that your team respects it.

Another is to bargain vigorously, dealing with every contingency before anything is signed. And once you have come to agreement, stand by a conclusion that was reached in good faith.

Donald Trump seems not to know, or care, about any of those rules. And, his attitude toward negotiation is resulting in global confusion.

North Korea: deal or no deal?

Last week, Trump announced plans to meet with Kim Jong-un, the North Korean leader whom he has belittled as "rocket man" and taunted mercilessly in Trump's first year in office.

The announcement, which came with little warning even to Mr Trump's Vice-President, seemed like a coup de grace for the mercurial American leader.

It would be the first time a US president had met with a North Korean leader, and seemed to spell a continuation of the thaw that began at the Winter Olympics, when North and South Korean athletes competed on blended teams.

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No sooner was the meeting announced, however, then the diplomats weighed in. They noted that North Korean leaders have wanted to meet with their US counterparts for decades, so it was hardly the victory that Mr Trump was claiming it to be.

They warned Mr Trump that he was in danger of being used by North Korea for propaganda purposes. And, they pointed out that Mr Trump had agreed to a meeting without knowing exactly why Mr Kim wanted to see him.

Suddenly, the White House backed away from its embrace of a no-strings meeting with Mr Kim. Now, the White House is saying that a meeting depends on the terms that can be reached.

It appeared that the deal to meet was now a no deal to meet. And, Mr Trump's behaviour was precisely in line with what those who know him have been saying all along.

Tony Schwartz, who wrote Mr Trump's autobiography, The Art of The Deal, says the President has an unshakable belief in his negotiating abilities. In fact, Mr Trump expressed that confidence to Jane Meyer of The New Yorker in 2016.

"I've made a fortune by making deals. I do that. I do that well. That's what I do," he told her.

TPP and NAFTA: deal or no deal?

Mr Trump also refuses to be pinned down until the last possible moment, Schwartz says. And even when a deal is done, it isn't done.

He has already proved that numerous times in just 14 months. As soon as he was in office, he pulled the plug on US participation in the Paris Climate Accords.

He pulled the US out of the meticulously crafted Trans-Pacific Partnership (which he now says the US may re-join, given that the nations have signed an agreement without the Americans).

He launched talks with Canada and Mexico to re-negotiate the North American Free Trade Agreement.

Did Canadian Prime Minister Justin Trudeau get the upper hand in negotiations on NAFTA? ( AP: Pablo Martinez Monsivais )

Australian steel: deal or no deal?

Last week, he shocked global leaders by imposing tariffs on steel and aluminium imports, which many economists said were superfluous, and could wind up hurting American industry more than it would help.

Initially declaring there would be no exceptions to the tariffs, by Friday, a new version was drafted, excluding Canada and Mexico, while the European Union and China also demanded their levies to be set aside as well.

After a flurry of conversations, Australia is now excluded as well, and there is some question about whether the country escaped in return for security considerations.

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It's easy to wonder where Australia stands with the US president, since the relationship has bounced from rocky over refugees to effusive praise last week.

"We have a very close relationship with Australia, we have a trade surplus with Australia, great country, long term partner, we'll be doing something with them," Mr Trump said in a cabinet meeting.

But no matter the public words of encouragement, it's only natural to wonder whether Mr Trump might wake up someday and turn on its ally with no warning.

Only last month, The New York Times was talking about a "reset" with Australia, with the nations sharing common concerns about China, trade and immigration.

And yet it's clear after tariffs, the environment, TPP, and North Korea that nothing is predictable about the American President, least of all his view of negotiations.

Three decades ago, the author Suzanne Massie taught Ronald Reagan a Russian proverb to keep in mind when he met with Soviet officials: "Trust, but verify."

Australian officials, and indeed any global leaders who deal with Mr Trump, might do well to remember another Russian saying:

"If you are given something, take it. If you are being beaten, run."

Micheline Maynard is an American journalist and author who has covered numerous sets of union, business and trade negotiations.