A summit of the world's top economies is set to open with leaders struggling over fall-out from a US-China trade war and bracing for the kind of divisive geopolitical drama that President Donald Trump often brings to the international stage.
The two-day annual gathering will be a major test for the Group of 20 industrialised nations, whose leaders first met in 2008 to help rescue the global economy from the worst financial crisis in seven decades.
The grouping now faces questions over its relevance to deal with the latest round of crises.
Overhanging the summit in Buenos Aires, the Argentine capital, is a bitter trade dispute between the US and China, the world's two largest economies, which have imposed tariffs on hundreds of billions of dollars of each other's imports.
President Donald Trump and First Lady Melania Trump arrive in Buenos Aires for the G20 summit. Source: AAP
All eyes will be on a planned meeting between Trump and Chinese President Xi Jinping on Saturday to see whether they can find a way to calm the waters and make progress toward resolving differences that threaten the global economy.
On the eve of the summit, G20 member nations were still racing to reach agreement on major issues including trade, migration and climate change that in past years have been worked out well in advance.
Trump's skepticism that global warming is caused by human activity has even raised questions about whether the countries will be able to reach enough consensus on the issue to include it in the summit's final communique.
Further clouding the summit is the escalation of conflict between Russia and Ukraine - a topic that will be on many leaders' minds when they see Russian President Vladimir Putin.
There are also questions about how to handle the awkward presence of Crown Prince Mohammed bin Salman. Saudi Arabia's de facto ruler arrived under swirling controversy over the murder of Saudi journalist Jamal Khashoggi in the Saudi consulate in Istanbul in October.
Argentinian President Mauricio Macri, his wife Juliana Awada with Canadian PM Justin Trudeau and Canadian First Lady Sophie Gregoire Trudeau. Source: AP
Before heading for Buenos Aires on Thursday, Trump said he was open to a trade deal with China, but added, "I don't know that I want to do it."
China is hoping for "positive results" in resolving the trade dispute with the United States, China's Commerce Ministry said on Thursday.
A slowdown in the global economy will worsen if Trump presses ahead with plans to further increase tariffs on some $US200 billion of Chinese imports to 25 per cent, OECD Secretary General Angel Gurria told Reuters.
Russian President Vladimir Putin. Source: AAP
While Trump's meeting with Xi is all but certain to go ahead, the US president on Thursday abruptly scrapped his planned talks with Putin, citing Russia's recent seizure of Ukrainian vessels.
One potential bright spot at the summit could be the signing of a revised US-Mexico-Canada trade pact.
But a day before the three neighbors were due to formalise the agreement on Friday, negotiators were still thrashing out what exactly they will be putting their names to, officials said.
