Mr Trump said: "You know, whether you like it or not - and it may not be politically correct - but we have a world to run and in the G7, which used to be the G8, they threw Russian Federation out". Moscow has denied the allegations.
Mr. Trump, though, said conversations were cordial and respectful at the summit.
The president has been a disruptive force for the worldwide trading order, insisting other countries move to reduce barriers he said have left the USA with a trade deficit of more than $800 billion.
Led by the USA, the group kicked out Russian Federation in 2014 over its annexation of Crimea and its support for pro-Russia separatists in Ukraine.
He described the trip as a "mission of peace".
Despite earlier reports of a rant over trade from Trump, he said the meeting "was not contentious" and called the relationships between the leaders "outstanding".
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Trump announced worldwide tariffs on steel and aluminum imports in March, with an an exemption for some trading partners. He was also very forceful when he shook the hand of the Japanese Premier Shinzo Abe at the White House in June 2017.
Trump planned to leave the summit before it ends on Saturday to head to Singapore for the next meeting on his schedule - a high-stakes summit with North Korean leader Kim Jong Un.
Trump said he pushed for the elimination of trade barriers, including subsidies and tariffs, at the G-7 meeting. "And I think on trade, there is a critical path, there is a way to progress altogether", he said, speaking in English. Prime Minister Justin Trudeau did not wait for the USA president to kick off the meeting in La Malbaie, Quebec.
President Trump's remarks were so free-wheeling that the panel on MSNBC's AM Joy wondered about his "state of mind".
As the leaders met, Trump played a wild card, suggesting that rather than both sides boosting retaliatory tariffs - as he has just done on steel and aluminium - they could declare for entirely free trade in the G7 zone.
"We have continued our cooperation even during hard times", Kurz said after his talks with Putin on Tuesday.
When a CNN reporter asked Trump about anger and frustration from USA allies over trade, he lambasted the reporter and his "fake friends at CNN". "I would say that the G-8 is a more meaningful group than the G-7, absolutely", he told reporters as he left the summit in Canada.
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The 33-year-old went on to win two National Basketball Association titles with the Heat before entering free agency again in 2014. Sources told ESPN that the injury was the result of James' punching a whiteboard in the locker room after that game.
In his final news conference before leaving, Mr Trump said trade was at the top of the agenda and the U.S. has been taken advantage of for decades and it cannot go on.
Still, a French official said on Friday the United States and European Union would establish a dialogue on trade within the next two weeks, signalling a modest step forward for the bitterly divided allies of the G7.
The US has slapped a 25% tariff on imports of steel and 10% on aluminium from countries including the United Kingdom and the rest of the European Union.
On Saturday, Trump repeated his desire to have a sunset clause in an updated NAFTA deal, a demand that Canadian Prime Minister Justin Trudeau has rejected.
Trudeau had made the issue of gender equality a priority for the gathering.
US President Donald Trump railed against trade practices he called unfair to the United States at a Group of Seven nations summit where leaders agreed on Saturday to fight protectionism and reform the World Trade Organisation.
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Other studies have found much higher rates of mental-health disorders among people at high risk of suicide, experts noted. A new study from the Centers for Disease Control and Prevention show almost 45,000 lives were lost to suicide in 2016.
At issue are new USA tariffs on steel and aluminum imports.