Ahead of the G20 Mr Trump told USA media he expected to go ahead with plans to raise tariffs on $200bn of Chinese goods - first introduced in September - to 25% (up from 10%) starting in January 2019.
In fact, 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.
In the two minutes of the Buenos Aires meeting open to the media, Mr Trump's first remarks suggested he was still coming to grips with the Australian leadership change that had now delivered the second prime minister of his presidency.
"As is typical at multilateral events, President Trump and the first lady had a number of informal conversations with world leaders at the dinner last night, including President Putin", spokeswoman Sarah Huckabee Sanders said. He said the European Union is expected to extend sanctions on Moscow over its "totally unacceptable" seizure of Ukrainian ships and their crews near the Crimean Peninsula.
He nevertheless described the Macri-Trump meeting as "extremely cordial" overall.
Secretary of State Mike Pompeo, however, separately met with Saudi Foreign Minister Adel al-Jubeir, the State Department said.
The presence of Saudi Arabian Crown Prince Mohammed bin Salman at the summit also made waves amid swirling controversy over the murder of Saudi journalist Jamal Khashoggi in the Saudi consulate in Istanbul on October 2.
"Don't worry", Prince Mohammed is heard saying in English to the French leader, who responds, "I do worry".
Saudi Arabia has denied that bin Salman played a role, but some leaders may be cool toward him to avoid seeming to legitimize a man who US intelligence agencies concluded ordered the killing.
US Trade Representative Robert Lighthizer earlier told reporters that Trump and Xi have a good personal relationship and "I would be very surprised if it (their meeting) was not a success".
According to Reuters, audio caught bin Salman telling Macron not to worry to which Macron replied, "I am anxious".
Trump threatens 25-percent tariff on imported cars
Trump, who has expressed anger over GM's closing of American auto plants this week, retweeted the tweet without comment. He also blamed many countries that had been exporting trucks to the U.S. of taking advantage of Washington for decades.
President Trump said recently that current tariff levels on $200bn (£157bn) of Chinese imports would rise as planned.
Mr Trump said he is hopeful for agreement at "some point".
Much of the president's reasoning for changing the North American Free Trade Agreement (NAFTA) was his claim that the agreement was so widely despised, and needed to be renamed.
Trump was also scheduled to speak with German Chancellor Angela Merkel and Turkish President Recep Tayyip Erdogan.
Moon's top press secretary, Yoon Young-chan, was quoted by the South's Yonhap news agency saying that Trump "asked that South Korea and the US closely cooperate so the next summit will be another historical milestone in the process of denuclearizing the Korean Peninsula".
The summit is focused on trade, but all eyes are on Trump's meeting with Chinese president Xi Jinping, which will be held on Saturday night local time.
British Prime Minister Theresa May's attendance at the summit marked the first time a United Kingdom prime minister has visited Argentina's capital.
But Human Rights Watch accuses him of responsibility and also of war crimes in Yemen, and on Wednesday, Argentine legal authorities took initial action to consider a request to prosecute him for alleged crimes against humanity.
"I believe in our capacity to make the spirit of dialogue and cooperation triumph", Macron said at a joint news conference with Macri, warning that if nations "close down", the alternative could be trade wars or armed conflict.
Officials familiar with the meeting's planning said Trump himself determined Navarro, who flew to Argentina about Air Force One on Thursday, should attend.
The next G20 summit will be held in Osaka, Japan.