OTTAWA - Leaders of the Group of Seven rich nations headed for a summit in Canada on Thursday more divided than at any time in the group's 42-year history, as US President Donald Trump's "America First" policies have created trade friction.

In a bid to rebuild America's industry, Trump has imposed tariffs on steel and aluminum imports, including those from key G7 allies like Canada, Japan and the European Union.

Trump has threatened to use national security laws to do the same for car imports and has walked back on environmental agreements and an international deal to prevent Iran from building a nuclear bomb.

French President Emmanuel Macron, who has invested in a warm personal relationship with Trump, said the other G7 nations - Great Britain, Canada, Germany, Italy and Japan, as well as France - should remain "polite" and productive but warned that "no leader is forever", a sign that Europe would not surrender meekly to the US president.

"Maybe the American president doesn't care about being isolated today, but we don't mind being six, if needs be," Macron told reporters. "Because these six represent values, represent an economic market, and more than anything, represent a real force at the international level today."

Canadian Prime Minister Justin Trudeau predicted "robust discussions" on trade, but other G7 members like Japan and Italy seemed less likely to want to challenge the US president.

Trump fired back soon after on Twitter, addressing both leaders directly, saying they were charging "massive tariffs" on US goods and had erected other trade barriers.

"I look forward to seeing them tomorrow," Trump wrote about Friday's start of the two-day summit.

Trump will come face-to-face with them at the gathering in Charlevoix, Quebec.

Trump signaled that he was in no mood to compromise as he met with Japanese Prime Minister Shinzo Abe, who has tried to cultivate a friendly relationship with the American president.

Trump raised the issue of US car imports with Abe at their meeting in Washington and said he wanted more investment in plants in the industrial heartland of Michigan, Pennsylvania and Ohio.

Abe is not the only world leader to have tried charming Trump and failed to come away with concessions from the US leader. Macron, who appeared to have built a warm relationship, said the "G6" leaders would not spark a fight at the summit.

"In this environment, above all we always have to stay polite, stay productive and try to convince (them) to keep the United States on board because they are our historical ally and we need them," Macron told a news conference with Trudeau in Ottawa.

-Reuters