Buenos Aires (CNN) President Donald Trump, convinced that he alone can break stalemates with adversarial counterparts on trade and security, will put his theory to the test in Argentina this week. Global markets and foreign capitals are eyeing him anxiously.

The G20 summit in Buenos Aires has become a fulcrum for Trump's high-stakes diplomatic gambles. By his own telling, positive meetings with the Chinese and Russian leaders this week could bring breakthroughs . But if the talks collapse, he's warned of dire consequences, including a prolonged trade war that would further roil global economies.

The heightened do-or-die drama fits well into Trump's reality show outlook on world affairs, even if it leaves other leaders uneasy. Already, the President has shown he's willing to throw a central moment of the global gathering into question, telling The Washington Post on Tuesday that he may scrap his planned meeting with Russian President Vladimir Putin over recent Russian aggression in Ukraine.

If it does occur, expert observers remain wary that the Trump-Putin meeting could result in a repeat of a maligned Helsinki summit in July that saw Trump forsake the US intelligence community's conclusions of Russian interference in the 2016 US election in favor of amplifying Putin's denials.

A day before he suggested his meeting with Putin might be off, Trump indicated to reporters there was blame for new tensions on the Ukrainian side, too, saying, "We do not like what's happening either way."

Putin is likely to make his case to Trump that Russia's decision to open fire and seize Ukrainian Navy ships was appropriate, and experts worry Trump will lap up that explanation as he did in Helsinki on election interference.

Diplomatic heavy lifting

Even if the Putin meeting does not happen, Trump's stay Friday and Saturday in the Argentine capital will still amount to one of his heaviest bouts of diplomacy since taking office. White House officials said he would meet with at least eight leaders during his trip, on top of the traditional G20 sessions, dinners and group photos.

Trump's isolation on the world stage is never more plain than at gatherings of his peers, including the yearly G7 and G20 summits that mark a US president's calendar. At two G7s and one G20, Trump has appeared at times out of sorts with top US allies. At a commemoration of the World War I armistice in Paris earlier this month, Trump walked to the ceremony alone, even as other leaders joined to walk together.

This time, aides have stacked the President's agenda with meetings separate from the G20 itself, placing him in back-to-back sessions that won't as easily highlight the rifts that have grown between some longtime US partners and him.

His meetings include Putin and China's Xi Jinping, along with his Argentine host, President Mauricio Macri, South Korea's Moon Jae-in, Turkey's Recep Tayyip Erdoğan, Japan's Shinzo Abe, India's Narendra Modi and Germany's Angela Merkel.

One leader he will not meet, at least not formally: Saudi Crown Prince Mohammed bin Salman, who has been castigated for his country's murder of journalist Jamal Khashoggi by many world leaders -- except by Trump, who pronounced the matter closed last week and said close US-Saudi ties would continue. The matter is likely to arise in Trump's talks with Erdoğan, who has pressed for greater punishment in response to the killing, which occurred at a consulate in Istanbul.

Unscripted for Putin, Xi?

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Trump's meetings with the Russian and Chinese presidents once again spotlight his belief in the power of personal diplomacy -- and how much he is willing to let ride on his ability to leverage personal relationships forged with world leaders to achieve his policy goals.

Rather than allowing his advisers to reach meticulously negotiated agreements that he can then cement in person, Trump is entering his meetings with Xi and Putin with no clear prearranged outcomes.

That same unpredictability resulted in Trump agreeing to on-the-fly US concessions in his meeting with North Korean leader Kim Jong Un last summer, including suspending joint US-South Korean military exercises. Pressed recently about how he is preparing for his meeting with the Chinese President, Trump offered the same response he had given ahead of the Singapore summit with Kim: "I've been preparing for it all my life."

Trump has made clear that his meeting with Xi could result in one of two dramatically different outcomes: a doubling-down of US tariffs on Chinese imports or a ceasefire in the trade war. What's clear is that it's all riding on the face-to-face meeting, one that will take place over a working dinner on Saturday evening that will mirror the time the two leaders met at Trump's Mar-a-Lago estate.

"There is a good possibility that a deal can be made, and that he is open to that," Trump's top economic adviser Larry Kudlow told reporters on Tuesday, citing a conversation he'd had earlier in the day with the President.

Other aides say Trump appears thirsty to strike some type of accord with Xi that would cause global markets to steady, even if the prospects for a full-scale trade agreement appear slim.

"President Trump and President Xi both have an incentive to put this dispute on hold," said Matthew Goodman, senior vice president and senior adviser for Asian economics at the Center for Strategic and International Studies in Washington.

Jittery markets are "putting a little bit of heat on President Trump to come to some sort of deal and not move ahead with tariffs," Goodman said. "For Xi Jinping, their growth is slowing and I think there's an interest in trying to get this behind them."

But it's the President's meeting with Putin that has most concerned administration officials and outside experts, who fear a Helsinki redux that could once again strengthen Putin's hand on the world stage.

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Despite his bravado, Trump has repeatedly demonstrated an aversion to face-to-face confrontations, particularly when it comes to US adversaries like Putin. This time, Trump is confronting fresh unrest in Ukraine, where Russian ships opened fire on and seized three Ukrainian vessels near Crimea over the weekend.

"The President meeting with Putin in the wake of this Kerch Strait incident is highly problematic for the United States, because there seems to be no question that the Russians were the aggressor here," said Nicholas Burns, a Harvard professor and former State Department undersecretary for political affairs, pointing to Trump's first statement in the wake of the incident appearing to blame both Ukraine and Russia.

Noting that Trump has "shown no ability to stand up to Putin," Burns predicted Trump would acquiesce to the Russian leader on the Ukrainian confrontation.

"Once again the United States is going to be in a position of looking weak, of not acting strongly in opposition to what the Russians are doing," Burns said.

Trump appeared to harden his stance on Tuesday, suggesting his meeting with Putin could be scrapped in the wake of the events in Ukraine.

"Maybe I won't have the meeting. Maybe I won't even have the meeting," he told the Post. "I don't like that aggression. I don't want that aggression at all."

The question now is how Trump will react once he finds himself in a room with Putin.

After his success in Helsinki, Putin could be looking for his latest opportunity to make his case directly to Trump and to see if he can get the same result, said Fernando Cutz, a former senior adviser to then-national security adviser H.R. McMaster.

And it just might work, Cutz said, noting the extent to which Trump can be swayed in these settings, calling it Putin's "best chance" because Trump "does not like confrontation at all, especially in person."

"Even silence on that topic would be a huge win for Putin. Anything short of the President coming out and condemning his actions in Ukraine to his face in front of the press would be a big win for Putin," said Cutz, who is now a senior associate at the Cohen Group, a consulting firm.

First presidential trip to Latin America

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Trump's visit to Buenos Aires for the G20 marks the first time he has set foot in Latin America since becoming President, a milestone he was scheduled to breach in April until he canceled a planned trip to Peru and sent the vice president in his stead.

His first visit to the region comes as he has once again stoked anti-immigrant sentiment in the US, portraying the caravan of several thousand Latin American migrants headed to the US to seek asylum as a dangerous threat to the country. While Trump sought to move beyond his Islamophobic campaign rhetoric during his first visit to the Middle East last year, there is no indication he intends to step back from his caustic comments about undocumented immigrants from Latin America during his visit to Buenos Aires.

Trump also won't be sitting down for a bilateral meeting with any other Latin American leader during his trip beyond Argentina's Macri, a friendly figure Trump first met several decades ago over real estate negotiations in New York. Trump was scheduled to make a stop in Colombia during his trip but he scrapped plans for a visit to the important South American ally for the second time.

Latin American countries have rallied behind the Trump administration's position on the political crisis in Venezuela, to which the President and top Cabinet officials have demonstrated a dedicated focus. But Trump's caustic rhetoric on immigration has also divided the region, weakening public support there for the United States.