Osaka, Japan (CNN) This weekend's G20 in Japan will be about as much fun for US President Donald Trump as bathing with a scouring pad. Even a man who enjoys confrontation as much as Trump can't be too excited at the failure that awaits him in Osaka.

And he really is doomed to failure in all kinds of areas. He hates the supranational DNA of the G20 and they abhor his divisive America First rhetoric.

The President's two-day ordeal will be made worse because he needs his fellow leaders' help in his latest showdown with Iran.

It almost came to war last week. After Iran shot down a US drone , Trump was ready to strike back with a retaliatory attack, only calling it off 10 minutes before it was due to launch. .

But having spent much of his presidency goading many of his fellow world leaders, he can expect little sympathy.

He wants to crush Iran's economy, cut its oil supplies to the world, and protect everyone else's ships in the Strait of Hormuz, but doesn't quite seem to know where to go from there.

In theory, there is no better place than a G20 to get support for an idea. It is a place where the President of the United States has other leaders practically tripping over one another for a meeting. And Trump has plenty of meetings.

The most anticipated of these is with Chinese President Xi Jinping. On this, the world holds its breath. Will they avoid tipping their trade war in to global recession? Rumors are they will have a meeting of the minds much as they did at the last G20 and, for now at least, hold off escalating their trade confrontation.

Trump is far less likely to get Chinese traction on Iran, in part down to its reliance on Iran for oil.

Trump's Iran problems don't stop with China. He'll meet with Vladimir Putin of Russia, whose foreign minister has accused Trump of "blackmailing" Iran.

The Putin meeting remains shrouded in mystery. "What I say to him is none of your business," Trump told reporters on the way to Osaka. He'll likely get short shrift if he does raise Iran: Putin is one of its biggest backers. And there are few things Putin wants more than to weaken the US grip in the Middle East and strengthen his own.

Trump will also meet the currently weakened populist President of Turkey, Recep Tayyip Erdogan. The idea he can break the Turkish strongman's steady relationship with Iran also seems like a long shot.

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Then there is his bilateral with Angela Merkel, the German Chancellor. She has marched lock step with the UK and France on Iran, criticizing Trump's unilateral withdrawal from the multinational nuclear deal.

Neither French President Macron nor outgoing British leader Theresa May are expecting lengthy meetings with Trump in Osaka. Both countries have blasted his collision course tactics with Iran, which have put them under pressure to help Tehran out financially in order to salvage the nuclear pact.

French officials say they see "no signal the US is interested in dialogue" with Iran and although they consider themselves "good allies" of the United States, they would not "automatically" follow Washington on Iran.

Indeed, Trump's biggest problem is convincing leaders he knows what he wants out of his escalation with Iran.

Iran's President Rouhani, not for the first time, questioned Trump's sanity this week, suggesting "the White House is suffering from mental disability".

Trump will have at least one less fractious meeting to look forward to, when he breakfasts on the last day with Saudi Arabia's Crown Prince, Mohammed Bin Salman.

Bin Salman wants Iran contained. But how the pair of them parlay their anti-Iranian passions into anything close to actionable in the Gulf is anyone's guess. No doubt the cost of it will figure in their calculations.

The one leader who might be able to help Trump, at a cost, is the host, Japan's savvy Prime Minister Shinzo Abe -- the world leader Trump has met more than any others.

He's the guy who ate hamburgers, played golf and signed baseball hats with Trump during a mini-bromance in Tokyo late 2017. A few days later, he ran roughshod over Trump's rejection of the 12-nation Trans Pacific Partnership and launched it with the remaining 11.

Like China, Abe also buys Iranian oil. By virtue of his country's unfortunate place in history, he is keener than most to make sure Iran's theocratic leaders never get their hands on nukes.

He went to Tehran the week before last and met with Rouhani and Supreme Leader Ayatollah Ali Khamenei. But just as he was trying to damp down tensions with the US, two tankers, one of them Japanese-owned, were attacked in the Straits.

Iran's mullahs face an existential threat to their theocracy from the tanking economy and need economic relief. If Abe can give them any glimmer of hope in this, it will come at a cost they have so far refused to pay: the adjustments Trump demands in the Iran nuclear deal.

The paradox Trump faces is that if he is forced to go it alone and continue ratcheting up tensions with Iran, he risks sparking a war and breaking a campaign promise by sending more troops to the Middle East.

Even before touching down in Osaka, Trump seemed to be backing down on Iran, perhaps wary of his already caustic G20 reception. He is reverting to type: having demanded change, then built up expectations of a war, he now declares a victory of sorts. Much as he done in the past with North Korean dictator, Kim Jong Un.