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The G20 summit is a glimpse at the future world order

Editor's Note: (Nic Robertson is CNN's international diplomatic editor. The opinions in this article belong to the author. )

Buenos Aires () If the G20 were a music festival, you'd be stressing about not being there.

The once snooze-worthy global power fest now looks like diplomacy on steroids.

Where else -- even pay-per-view pales in comparison -- will you get so many heavyweights waiting to face off: Vladimir Putin and Donald Trump; Donald Trump and Xi Jinping; Donald Trump, Justin Trudeau and Mexico to see if they can sign Trump's revamped NAFTA agreement, to name just three.

Trump, who normally shuns international travel, is turning the event into a one-stop diplomatic shop, with seven bilateral meetings scheduled in 48 hours.

Not yet on the agenda: a meeting between Trump and Theresa May, but it will be worth watching the body language when they do cross paths. Just this week, Trump publicly criticized her Brexit deal, saying it makes the prospect of a trade deal between the United States and the United Kingdom post-Brexit unlikely.

If you are minnow, even a big one like May, Trump is a dangerous ally, even on a good day. Just ask German Chancellor Angela Merkel. She's down for a one-on-one with Trump, and it's hard to remember the last time he didn't try to undercut her just before they met.

But this year's breakout star will be Saudi Arabia's Crown Prince, Mohammed bin Salman. Pretty much any leader he meets will be an event in itself.

Did they smile? Did they shake hands? Did they broker any deals or sign any new ones? And did any of them give bin Salman a dressing down over the brutal killing two months ago of Jamal Khashoggi? And if not, why not?

The meetings are endless. Access, sadly, is harder come by than a Rolling Stones backstage pass. Even if you get one, it will need to come with an accompanying unicorn so you can jump the tedious rings of security.

Still, this is the place to be.

It's the type of weekend when rumors are legion and facts tantalizing.

How big was Putin's grin? Did bin Salman get the cold shoulder -- and was he about to leave before it all began? Did Xi blink? And which leader most drew Trump's ire? Merkel and Trudeau know all about that.

A lot of people will be hoping it's not Xi. In bad news for world trade, both he and Trump seem set on course to escalate a trade war.

Unlike Trump, whose gut seems to guide him from hour to hour, the Chinese leader is likely thinking a few years ahead. He is a leader for life and will be attending G20 summits long after Trump's time in charge is history.

But that won't matter this weekend in Buenos Aires. The consequences of this meeting could cement a legacy that will put the condo salesman-turned-"very stable genius" President into the annals of 21st-century economic history.

Then there is Putin, who always seems to be able to conjure a fresh crisis as he lands on the world stage -- this time accused of shooting up Ukrainian ships in the Kerch Strait.

Trump has canceled his meeting with the worryingly provocative Putin. This means they won't get to discuss all of the crucial issues that John Bolton suggested they might, from arms control to the Middle East.

Putin grinned as he left his last meeting with Trump. Now he will have to leave the G20 unsure if the US will interfere in Ukraine as Russia tightens the screws on Kiev's sovereignty in the Azov Sea.

Xi and Trump will be the next big-ticket meeting to watch. As I've mentioned, there is a lot at stake. This is one on which world trade may swing or sag.

Trump told The Wall Street Journal on Monday he is ready to impose tariffs on another $267 billion dollars of trade with China and indicated he is unlikely to not increase tariffs on another $200 billion of trade from 10% to 25% next year.

His economic adviser tried on Tuesday to inject some optimism into the meeting, saying there is a "good possibility" a deal can be made if "certain conditions" are met on "fairness and reciprocity," including on issues of intellectual property, technology, ownership issues and tariffs. But Xi has been staring down that same demand since trade talks began.

Blink or fold, it may be like watching paint dry, but both men need to walk away winners if we are all to benefit.

Trump's meeting with bin Salman is being downgraded. Not a full meet-and-greet, according to Bolton, although Sarah Sanders said she "won't rule out" some "interaction."

It's still one to watch. The Saudi Crown Prince has already had some kind Trumpian blessing for his role, whatever it may be, in the Jamal Khashoggi affair in the form of a rambling White House statement last week that said he "may or may not" have ordered the journalist's killing.

On Saudi minds will be the question: Will Trump find some way to embarrass bin Salman through his enthusiastic embrace?

The expected meeting between bin Salman and Turkish President Recep Tayyip Erdogan will be unlikely to resolve once and for all how and why Khashoggi was killed -- and more importantly, what happened to his body.

If that were to happen, there will be plenty more smiles in the obligatory so-called family photo, which is usually a lackluster affair.

Trump's various meetings will no doubt be focused on his America first policy, especially on trade. This is likely to kill any chance of a substantial communique, usually the big show at these summits.

It's what stymied agreement a few weeks ago at the Asia-Pacific Economic Cooperation summit and last summer at the G7.

Trump's abhorrence of multilateralism is taking its toll and creating global drama, right out of "The Apprentice" playbook. Ratings for this G20 may well go up.

Only a brave punter would put money on Theresa May surviving her Brexit turmoil at home and making it to the next G20 gig.

Angela Merkel will, too, be wondering if this is her final rodeo. German politics are febrile right now, and her steady step is faltering.

See, so much to keep your eyes on. Who's up, who's down, who's in, who's out. So, don't fall asleep; you might just miss the one they all end up talking about.

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