U.S. President Donald Trump, who is due to attend the leaders' meeting in the Canadian province of Quebec, imposed tariffs last week of 25 percent on steel and 10 percent on aluminium from Canada, the EU and Mexico, citing national security reasons.
A senior Canadian government official said discussions on the global economy on the first day of the summit, which is scheduled for Friday and Saturday, would quickly turn to trade issues.
"There will be disagreements on important issues and tariffs will certainly be one of them," the official told reporters.
"We won't be hiding the fact that we disagree on some of these issues and that's the value of the G7, is to be able to have these frank discussions between leaders."
G7 finance ministers met last week and rebuked Washington over the tariffs, setting up a fight at the G7 summit.
Canadian Prime Minister Justin Trudeau's position on the punitive measures would remain "consistent and clear" during talks at the summit, the official said.
Canada, the No. 1 steel exporter to the United States, said last week it would impose retaliatory tariffs on C$16.6 billion (9.55 billion pounds) worth of U.S. exports and challenge the U.S. steel and aluminium tariffs under the North American Free Trade Agreement and the World Trade Organization.
The G7 groups Canada, the United States, Japan, Britain, Italy, France and Germany. The European Union also attends.
The Canadian official said Trudeau intended the summit to focus on themes such as economic growth that benefited everyone and increasing gender equality.
But the question of tariffs - as well as the U.S. decision to pull out of a deal designed to curb Iran's nuclear ambitions - is what most G7 members want to sort out.
In Berlin, a German official said European G7 members would present a united front on issues from Iran to trade and climate change but did not know whether leaders would agree on a final communique.
In Brussels, a senior European Union official said the bloc had "extremely low expectations for the G7 summit" and did not foresee a breakthrough on the tariffs.
Trudeau is expected to hold one-on-one meetings with all of the attending countries' leaders, the official said, although he did not answer directly when asked by reporters if a communique would be issued at the end of the summit.
(Leah Schnurr and David Ljunggren; Additional reporting by Paul Carrell and Andreas Rinke in Berlin and Jan Strupczewski in Brussels; Editing by Susan Thomas and Peter Cooney)
By Leah Schnurr and David Ljunggren
