Trudeau is scheduled to meet with Trump at 5 p.m. on Friday, the official said at a press briefing in Quebec.
The G7 Summit has been largely overshadowed by Trump's attempts to organize a summit with North Korea in the coming days.
"A trade war doesn't spare anyone", Macron said.
In the US, farmers fear the tariffs will hit them earliest and hardest. "And we don't want there to be one".
Pictures of Mr Trump's daughter Ivanka gazing intently at Trudeau seemed to underline the cosiness between the two neighbours.
G7 leaders have praised the U.S. president for his efforts to stabilise the Korean peninsula, but are unhappy that he pulled out of the Iran nuclear deal.
Trump's first meeting at the summer resort on St Lawrence river is with his French counterpart, Emmanuel Macron, followed by sessions with the full summit, and then a bilateral with the host, Justin Trudeau, in the early evening. "Look forward to seeing them tomorrow".
US President Donald Trump has grown exhausted of Theresa May's "school mistress" tone, the president's allies say amid fears that the pair will not hold talks in Canada. In response, Trump quipped to Trudeau, "Didn't you guys burn down the White House?" referring to the War of 1812.
G-7 leaders are meeting Friday and Saturday in what's shaping up to be the most divisive gathering of leaders from major industrialized nations in years. The member countries are Canada, France, Italy, Japan, Germany, the United States and Britain. The European Union also attends. The Trump administration has also clashed with Canada over his insistence that the 24-year-old North American Free Trade Agreement involving the United States, Canada and Mexico be written to better serve the U.S.
The U.S. and the rest of the G-7 countries depend on each other for security and as economic partners, so the governments will have incentives to find some common ground. France's finance minister described the group as "far more a G-6 plus one than a G-7".
"The six countries of the G7 without the United States, are a bigger market taken together than the American market", Macron said.
There is no evidence that Trump, who says his hard line on trade is necessary to protect US industry and workers from unfair global competition as part of an "America First" agenda, will tack a conciliatory direction at the summit.
Mr Trump does not intend to withdraw from Nafta, National Economic Council director Larry Kudlow said on Fox & Friends.
The fallout from Trump's imposition of steel and aluminum tariffs on his G7 partners, as well as broader disagreements on trade and climate change, was also fuelling the G6-plus-one divide that has the US increasingly offside with its allies.