"I've been firm, I've been clear, but I don't think descending into insults is right for the way Canada engages with the world", the prime minister said. Otherwise, "we're going to make a deal directly with Canada, directly with Mexico".
"Very dishonest & weak", Trump said, adding that recently imposed USA tariffs on imports of Canadian steel and aluminium were in response to similar measures imposed on American dairy products by Canada.
In a statement issued following Mr Trump's tweets, Mr Trudeau said he remained focus on what was accomplished at the G7 summit. Mr Trump left the summit early for Singapore, where he will meet North Korean leader Kim Jong Un next week. Trump had at one point proposed that G-7 nations eliminate all tariffs, barriers and subsidies.
He spoke of the importance of educating girls in remarks at the start of the meeting, which included his fellow G7 leaders and Christine Lagarde, the managing director of the International Monetary Fund.
A French presidential source said Trump's proposal did not seem "coherent" in view of the latest economic sanctions imposed by the United States on Moscow.
Mr. Trump said on Saturday that he had told the G7 leaders that the USA required fair access to markets and an end to unfair trade practices.
Trump also repeated an earlier proposal that US trading partners should drop all trade barriers, including tariffs and subsidies to industries and producers in their own countries. A frenzied effort last month to reach a deal that could pass the current U.S. Congress by the end of this year has stalled, in part after Trudeau's final push ran up against Trump's insistence on a five-year sunset clause that would see the pact renegotiated or killed after five years.
On the North American free-trade negotiations, Mr. Trump said he proposed a bilateral deal to Mr. Trudeau, an idea the prime minister rejected.
The president met with leaders from Canada, Britain, Italy, France, Germany and Japan in Quebec, where trade talks dominated the summit. It is the second time that Trump refused to join his G7 counterparts in committing to the accord.
But while Trudeau's months-long effort to reach out to US politicians and business leaders at every jurisdiction and level may not have won over Trump, it may pay dividends if Trump's attack finally spurs support from business groups or Congress.
"The rhetoric has far outpaced the implementation", said Geoffrey Gertz, trade analyst with Brookings think tank in Washington. Trump said he had not spoken with Russian President Vladimir Putin in a while.
Trudeau said he and Trump have disagreed over Trump's call for Canada to open up its supply management system, which protects dairy, poultry and eggs farmers, during the hard ongoing renegotiation of the North American Free Trade Agreement.
Canada has given up slices of its dairy market in previous talks, including with the U.S. on the Trans-Pacific Partnership, a pact Trump quit.