"We'll either leave it the way it is as a threesome deal" and "change it very substantially", Trump said Saturday in La Malbaie, Quebec, speaking to reporters before departing the Group of Seven leaders' meeting.
Canadian Prime Minister Justin Trudeau announced he told President Trump he will go through retaliatory tariffs after Mr. Trump's decision not to exempt allies such as Canada from tariffs on steel and aluminum imports.
Canadian Prime Minister Justin Trudeau called USA metal tariffs "insulting" and announced retaliatory measures.
During his press conference on Saturday, Trump warned foreign countries not to retaliate against the USA tariffs.
The tit-for-tat dispute over US metals tariffs followed more than a year of tense and so far unsuccessful negotiations to renew NAFTA and a long and failed charm offensive by Trudeau and top Canadian officials to avoid Trump's trade ire.
The G7 summit came amid rising tensions between the USA and other member nations - Canada, Britain, France, Germany, Italy, and Japan - over Trump's recent steel and aluminum tariffs.
Trump also repeated an earlier proposal that USA trading partners should drop all trade barriers, including tariffs and subsidies to industries and producers in their own countries.More news: Warriors sweep away Cavaliers to repeat as National Basketball Association champions
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"Trump came late, he's leaving early and he gave no ground whatsoever", Al Jazeera's John Hendren, reporting from Quebec, said.
This year's G7 summit, which begins Friday in Canada, is set to be unusually ill-tempered, with the US facing off against the other six in the group: Germany, France, Italy, Canada, Japan and the United Kingdom. Mr Trump said the move would protect domestic producers that were vital to U.S. security.
Trump says they will either have a better agreement on NAFTA or two deals involving separate trade deals with both Canada and Mexico.
Russian Federation was suspended from the group in 2014 because of its annexation of Crimea from Ukraine.
While Trump set a combative tone before even arriving at the summit with tweets about unfair trade deals, he appeared affable and joking at multiple brief photo opportunities and praised Macron for helping to work out trade issues.
He also denied the summit had been contentious, a remark that contradicted what one G7 official described as an " extraordinary" exchange on Friday in which Trump repeated a list of trade grievances, mainly concerning the European Union and Canada. Why are we having a meeting without them?
"Maybe the American president doesn't care about being isolated today, but we don't mind being six, if needs be", said the French President. Trump left the summit early for Singapore, where he will meet North Korean leader Kim Jong Un next week. In a statement at the time the countries, which include the U.S., France, Canada, Germany, Italy, the United Kingdom and Japan, condemned Russia's actions as "illegal" and in "contravention of global law".
If leaders were "cordial" with Trump he may have taken it the wrong way.