Later, the USA president tweeted: "Prime Minister Trudeau is being so indignant, bringing up the relationship that the USA and Canada had over the many years and all sorts of other things...but he doesn't bring up the fact that they charge us up to 300% on dairy - hurting our Farmers, killing our Agriculture!"
He was reacting to Trudeau's declaration that Canadians would "not be pushed around" and would hit back at punishing USA tariffs on metal imports with "equivalent tariffs".
President Trump did the courtesy to Trudeau to travel up to Quebec for that summit.
The issue of trade was the most controversial heading into the G7 summit in La Malbaie, Que., with Trump launching multiple barbs in Canada's direction in the days leading up to his arrival. Mr Trump said the move would protect domestic producers that were vital to U.S. security.
David Akin wonders if Canada and its G7 allies can trust the U.S.?
The president refused to sign a solidarity agreement with the other G7 members and suggested more tariffs could be in the works.
"As Canadians, we are polite, we're reasonable, but also we will not be pushed around,"Trudeau said".
Trump's renewed comments on trade come amid a growing dispute between Washington and its top allies.
Trump has threatened to impose tariffs on certain products in response to trade barriers put in place by other countries.
Mr Trump's looming summit with North Korean leader Kim Jong-un heightened tension, and White House economic adviser Larry Kudlow accused Mr Trudeau of betraying Mr Trump with "polarising" statements on trade policy that risked making the United States leader look weak on the eve of the historic North Korea summit. "We can't pose a security threat to the United States and I know that the Americans understand that".
While other presidents and prime ministers have had testy relations - president Richard Nixon famously used a profane word, behind closed doors, to refer to Trudeau's father Pierre Trudeau, also in the context of trade talks - neither side has demonstrated this level of animosity since John Diefenbaker feuded with John F. Kennedy in the early 1960s.
Kudlow, in a separate TV appearance, said Trudeau was "polarizing" and "really kind of stabbed us in the back".
Bruce Heyman, the former U.S. Ambassador to Canada, on Monday slammed Donald Trump's treatment of Justin Trudeau, and Canada in general, demanding the president apologize for his surrogate's claim there's a "special place in hell" for people like the Canadian prime minister.
"I don't blame them, I blame our leaders", he said.
"Justin Trudeau's left eyebrow detached after meeting Trump - so what?"