After violent protests marred last year's G20 summit in Germany, Argentine police, coast guard and border patrols cordoned off a 12-square-kilometer (5-square-mile) area around the riverside Costa Salguero convention center.
In tweets on Thursday afternoon, US President Donald Trump abruptly called off a planned meeting with Russian President Vladimir Putin over Russia's seizure of Ukrainian navy ships in disputed waters off the Crimean peninsula on Sunday. In addition, at least 3,000 journalists are following the meeting.
The US-China trade war has eclipsed the two-day G-20 gathering with the world wondering if Trump and Xi can reach a truce on a dispute that has rattled markets.
One potential bright spot at the summit could be the signing of a revised US-Mexico-Canada trade pact.
Canadian Prime Minister Justin Trudeau called on Trump to remove tariffs on steel and aluminum, saying they remain a major economic obstacle.
Trudeau still had a few barbs on Friday. US Secretary of State Mike Pompeo said he had seen no "direct" evidence linking the prince to Khashoggi's murder at a Saudi consulate in Turkey. He's been unnerved in recent days by a shaky stock market and factory closures by General Motors, according to people familiar with the matter, and is hoping to be able to tout the new trade agreement in Argentina.
Chinese President Xi Jinping and other leaders from the BRICS group of leading emerging economies, Brazil, Russia, India, China and South Africa, all called for an opening of worldwide trade and a strengthening of the World Trade Organisation (WTO). Trump has known Macri for decades, beginning when both were real estate developers.
The president has had a long-standing relationship with Argentina's leader prior to their time in politics. "He was a young man, a handsome man".
The Kremlin said it had not been notified and only learned about it from the tweet. "Little did you realize I would become president".
White House spokesperson Sarah Sanders insists the reason for the cancellation was the situation with Ukraine, but said the probe into possible collusion between the Trump presidential campaign and Russian Federation was damaging ties between the two countries.
Meanwhile, French President Emmanuel Macron hinted that he would raise the issue of the murder of Saudi journalist Jamal Khashoggi when he meets Saudi Crown Prince Mohammed bin Salman, whom the Central Intelligence Agency reportedly concluded had ordered the killing.
Trump has taken the opposite approach, indicating he has no plans to cut ties to Saudi Arabia.
Security concerns also weighed on the two-day talks in Buenos Aires. Putin used the time set aside to meet with Trump to pow-wow with Turkish President Recep Tayyip Erdogan. It is also the first to be held in South America.
Japanese Prime Minister Shinzo Abe also spoke at the press availability with Trump ahead of their meeting.
"I'm not here to critique or second-guess the Chinese economy, but most observers believe China to be in a slump, whereas the United States is in a very strong, solid position going into this summit".
What Mr Trump appeared to lack in understanding of events within the Liberal party room, he made up for in enthusiasm towards Mr Morrison's achievements in his first three months in office.
Mrs Merkel's own arrival at the summit has been delayed by a technical fault in her plane.
Trump has yanked the United States out of the landmark Paris climate accord.
The President's global trips have been repeatedly marred by developments in the investigation, beginning with Mueller's appointment as special counsel just two days before Trump left for his first worldwide trip. In previous years, the G20's joint statement had been hammered out well in advance. A year later, as the President prepared to fly to Helsinki to meet with Putin, the Justice Department announced the indictment of Russian intelligence officers linked to election interference. Russia's foreign minister regretted the move, but said "love can't be forced".
Scrapping the meeting with Putin, though, did not eliminate all of the President's flair for make-or-break drama.
Navarro's presence at the dinner might signal an agreement is less likely, though Trump has suggested the final result of the meeting will largely depend on the leaders themselves.
Later in the one-minute clip Mr Macron says: "You never listen to me" and the Crown Prince replies: "I will listen, of course".