French President Emmanuel Macronsaid he and Trump had "open and direct" discussions, adding that he thought there was a way to get a "win-win" outcome on trade.
Trump posted his comments from Air Force One as Canada was releasing the official communique that had been endorsed by all seven leaders.
In the communique announced by Canadian Prime Minister Justin Trudeau, the group of major industrial nations - Canada, the USA, the UK, France, Italy, Japan and Germany - agreed on the need for "free, fair, and mutually beneficial trade" and the importance of fighting protectionism. Canadian Prime Minister Justin Trudeau has sat patiently through several rounds of talks to renegotiate NAFTA, only to see Trump repeatedly threaten to tear up the agreement if Ottawa doesn't agree to what it sees as unreasonable demands.
President Donald Trump departed the Group of Seven summit early Saturday without making any trade concessions and declared the leaders of the industrialized countries have treated the United States as "piggy bank" to be robbed.
UK Prime Minister Theresa May stood with Trudeau on the issue of trade.
"It's going to change", said Trump. "I blame, as I said, I blame our past leaders for allowing this to happen", he said.
In his tweets Trump called Trudeau "dishonest and weak", "meek and mild" and accused him of lying.
Trump, who angered Washington's top allies last week when he imposed tariffs on steel and aluminium imports from Canada, the European Union and Mexico, issued a broad indictment of global trade, with swipes at the G7 and India.
Other G7 leaders, including British Prime Minister Theresa May and German Chancellor Angela Merkel, have also spoken out against the US tariffs.
"It will take much longer to rebuild that trust".
It is an annual summit bringing together Canada, the United States, the UK, France, Italy, Japan and Germany, which represent more than 60% of global net worth between them. The country was expelled after its annexation of Crimea in 2014. "We are focused on everything we accomplished here at the #G7 summit", spokesman Cameron Ahmad said. Readmitting Russia to the group would be an "asset", according to the president.
Trump departed the annual G7 gathering after arriving late to a breakfast on gender equity and skipping later sessions on climate change, clean energy and ocean protection.
The president's sharp comments came as he is now en route to Singapore for a highly anticipated meeting with North Korean leader Kim Jong Un, set to be held on Tuesday.
"I have made it very clear to the President that it is not something we relish doing, but it something that we absolutely will do", Mr. Trudeau said. "That's what I do". The non-factual part of this is - they have enormous tariffs. Roughly 28,000 American service members and civilian military personnel are now stationed in South Korea.
The US president repeated his call for Vladimir Putin to join the other leaders around the summit table.
Because the USA has vowed to ignore the rules of the global trading system that it helped put into place, including the World Trade Organization, trade deals are stalled for the foreseeable future. The likes of Republican Senator John McCain and Alberta's conservative leader Jason Kenney both spoke out in defence of Trudeau yesterday.