Leaders of the Group of Seven rich nations headed for a summit in Canada more divided than at any time in the group’s 42-year history, as US president Donald Trump’s “America First” policies risk causing a global trade war and deep diplomatic schisms.

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

Mr 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 Mr Trump, said the other G7 nations - 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,” Mr 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,” Mr Trump wrote about Friday’s start of the two-day summit. Trump will leave the summit on Saturday morning, before the event has concluded, and fly to Singapore for his historic meeting with North Korean leader Kim Jong Un on Tuesday, the White House said in a statement late on Thursday.

The G7 leaders will meet in a luxury cliff-top hotel in the town of La Malbaie, about two hours’ drive from Quebec City. The site has been sealed off by police, making demonstrations impossible.

Several hundred protesters - some wearing red flags and red masks - walked noisily through the streets of Quebec City on Thursday evening, heading for the Congress Center where the media are based. Some in the crowd, closely watched by riot police, carried banners with slogans such as “The G7 does not represent us.” Others carried posters with defaced photos of Trump. The US president will come face-to-face at the gathering with world leaders whose views do not chime with his on a range of issues from trade to the environment as well as Iran and the construction of a new U.S. embassy in Jerusalem.

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