The two-day annual gathering will be a major test for the Group of 20 industrialized nations, whose leaders first met in 2008 to help rescue the global economy from the worst financial crisis in seven decades, but which now faces questions over its relevance to deal with the latest round of crises.
Protesters have vowed a mass rally later Friday, underlining security concerns after recent football violence forced the relocation of a showpiece final to Spain.
Modi told Xi that he was looking forward to host him for an informal summit next year. Trump wrote on Twitter. If we can make a deal that'd be good.
Investigator Robert Mueller revealed that former top Trump aide Michael Cohen had admitted direct communications with Putin's office. A meeting with Trump has not been ruled out by the White House.
Any easing of tensions on trade could ease gains in the U.S. dollar and boost riskier assets including emerging-market currencies and stocks, though investors and analysts agree that the USA and China are trying to fix a long-term problem that cannot be solved in one dinner.
"We can't resolve problems such as the future of work or climate change issues on our own", said Mr Macri.
The trade conflict between the world's two largest economies has seen a 6 percent slump in the onshore yuan against the greenback this year, raising speculation that China has deliberately weakened its currency and drawing Trump's ire.
Trump counted a victory Friday for his brash strategy as the United States, Canada and Mexico signed a new trade deal, a successor to the North American Free Trade Agreement. The two leaders are expected to discuss the ongoing trade war, with new U.S. tariffs on Chinese goods set to kick in next month.
British Prime Minister Theresa May, speaking to Sky News before the summit, said she would press the crown prince both on Yemen and Khashoggi at the G20.
"We've already spoken and we're working very hard", Trump told reporters Friday in Buenos Aires, when asked about his upcoming meeting with the Chinese president.
Among the other leaders at the summit will be Saudi Crown Prince Mohammed bin Salman, the focus of tensions over the murder of one of his prominent critics in October.
Saudi Crown Prince Mohammed bin Salman and Vladimir Putin.
A joint declaration is expected to be published at the end of the summit on Saturday.
But on climate change, the United States once again marked its differences with the rest of the G20 by reiterating in the statement its decision to withdraw from the Paris Agreement and its commitment to using all energy sources. His opposition to collective action stands in defiance of scientists' increasingly urgent warnings that policy action is desperately needed to counter the climate threat.
In the short term, USA tariffs and the trade war would increase uncertainty for Chinese investment and durables consumption, according to Goldman.
Demonstrators gathered near the National Congress building in Buenos Aires and protested against the G20's failure to address a broad range of issues, from climate change to poverty.
U.S. objections on those fronts have seen two major summits this year, of the Group of Seven democracies and the Asia-Pacific Economic Cooperation forum, end without the once-routine statements.
"Will we even have a communique?"
"Everyone agrees that the WTO should be reformed", Merkel said.
US President Donald Trump and Chinese President Xi Jinping (習近平) were yesterday to sit down for dinner and their table talk will undoubtedly have a global impact.
Argentines are grappling with soaring inflation and unemployment.
They paraded with signs attacking Trump and the International Monetary Fund, whose largesse is keeping Argentina afloat at the cost of hard-hitting austerity measures.
But a day before the three neighbors were due to formalize the agreement on Friday, negotiators were still thrashing out what exactly they will be putting their names to, officials said on Thursday.
The government is vowing zero tolerance of violence as it hosts its biggest ever worldwide gathering.