China, which has already slapped tariffs on US$110 billion in USA goods, is likely to retaliate, ramping up a conflict that has already rattled financial markets and caused forecasters to downgrade the outlook for global economic growth.
"We are in a position to deal with it and handle it very well", he told reporters.
British Prime Minister Theresa May's attendance at the summit marked the first time a United Kingdom prime minister has visited Argentina's capital. I think they want to.
Two European officials involved in the discussions said the U.S. is hampering progress on both matters. He called the deal by its old name NAFTA, prodded Trump over USA steel and aluminum tariffs and said General Motors Co's decision to cut production and its North American workforce, including in Canada, was a "heavy blow".
With a rise in nationalist sentiment in many countries, the G20 - which accounts for two-thirds of the global population - faces questions over its ability to deal with trade tensions, which have roiled global markets, and ease geo-political disputes.
In 2008, amid the global financial crisis, it evolved into what it is today: a major forum for dialogue and decision-making attended by world leaders from vital economies.
The United States and China are locked in a dispute over their trade imbalance and Beijing's push to challenge American technological dominance.
Xi also reiterated that his country will continue to "open up", protect intellectual property rights and encourage fair play - all of which have been identified as problems by the U.S. government.
Host country Argentina was caught between the two powers on Friday when the White House claimed that Buenos Aires agrees with Washington that China's trade policies are "predatory".
After initial plans for him to stay away from the summit, Trump's hardline trade adviser, Peter Navarro, was added to the USA delegation at the last minute and is expected to attend the meeting between Trump and Xi, a U.S. official and a source familiar with the situation told Reuters.
In the run-up to November 6 congressional elections, Trump ramped up criticism and accused China of interfering domestically to hurt his Republican Party.
Trump later said "we had no discussion", though he held out the prospect of spending more time with the crown prince.
Australia and USA reaffirm economic ties at G20.
He secured the support for the new agreement both of Prime Minister Justin Trudeau and Mexico's incoming leftist president, Andres Manuel Lopez Obrador. Oil prices have slid in recent weeks on concerns of softening global growth caused by the US-China trade war. "The US should give its habitual winner-take-all approach to worldwide relations the weekend off", it said.
The Trump administration is understood to be preparing new restrictions on Chinese nationals applying for places at American universities as part of an effort to curb spying.
A French source said that European leaders were trying to forge a statement on climate change even without the United States.
Trump was attacked for destroying the group's past unity on trade and climate change.
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.
But fallout from the Russian Federation collusion probe followed Trump to Buenos Aires, where the USA president cancelled a long-awaited meeting with President Vladimir Putin and tweeted furiously about latest legal developments back home. However, all eyes are on the Trump-Xi dinner meeting on Saturday, wherein the current trade tension is expected to dominate the proceedings.