Russian Federation is committed to deepening practical cooperation and coordination with China to safeguard global peace and security and build an open world economy, Putin said.
Protesters have vowed mass rallies to harangue the world leaders gathering in crisis-hit Argentina, where recent violence between rival football fans raised questions about the police's ability to control unrest.
PM Lee said Singapore and Buenos Aires would benefit from more exchanges of ideas on areas of mutual interest, and invited Mr Larreta to visit Singapore to learn more about Singapore's policies in security, urban development and Smart Nation programmes, said a statement from the Prime Minister's Office (PMO) on Thursday. Trump wrote on Twitter.
But in a rhetorical olive branch to Trump, Xi pledged at the G20 to do more to open up China's economy.
Investigator Robert Mueller revealed that former top Trump aide Michael Cohen had admitted direct communications with Putin's office.
Speaking in the White House before he left for the summit, Mr Trump tempered expectations. But enough has been tweaked for Trump to declare victory on behalf of the United States workers he claims were cheated by NAFTA.
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.
Trump suggested to reporters just before the sit-down that at "some point" it could yield "something that will be good for China and good for the United States". He has threatened to raise tariffs on 200 billion dollars' worth of Chinese imports from January.
Leaders during the G20 summit on Friday.
The German Chancellor's summit schedule was disrupted after a technical fault meant she had to change planes en route, delaying her arrival.
But ahead of what is seen as the most important meeting of USA and Chinese leaders in years, both sides said differences remained, and the outcome of the talks were uncertain.
Earlier, Putin grinned broadly and welcomed Saudi Crown Prince Mohammed bin Salman like a long-lost friend with an enthusiastic hand-shake after the group photo, where Trump looked on sombrely and Xi stood impassively.
Khashoggi was killed in the Saudi Embassy in Istanbul Oct. 2, a death that shocked many world leaders sitting around the table with bin Salman at the G-20.
Trump said his predecessor's passing would prevent him holding a post-summit news conference scheduled for later Saturday, "out of respect" for the Bush family. "Climate sustainability requires urgent collective action to prevent jeopardizing our future and that of generations to come".
Meanwhile, the USA reaffirmed its intention to withdraw from the Paris climate accord as other members of the group repeated their commitment to implement the Paris deal, taking into account their national circumstances and relative capabilities.
United Nations chief Antonio Guterres said in Buenos Aires that "this is a make-it-or-break-it moment" on the issue.
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.
The pair high-fived and shared a laugh, as the leaders of 19 countries and the European Union came together to hear the summit's opening remarks from Argentina's President Mauricio Macri.
Argentines are grappling with soaring inflation and unemployment.
The communiqué, which was finalized after delegates worked through the night on Friday, recognized trade as an important engine of global growth but made only a passing reference to "the current trade issues", without providing any details.
"There's a lot of people who don't have houses and don't have work".
Saudi Arabia's de facto ruler, who arrived amid controversy over the murder of Saudi journalist Jamal Khashoggi, has been ignored by other leaders at public events, although he has had a series of bilateral meetings with them in private.
The government is vowing zero tolerance of violence as it hosts its biggest ever worldwide gathering, and says it has won promises from the protest organizers to keep the streets calm.