The nine justices of the US Supreme Court will soon rule on the validity of President Donald Trump’s tariffs, a showdown that could blunt what the US leader claims is his favourite economic and diplomatic tool.

The dispute centres on two lawsuits filed by seven small businesses and 12 US states, led by Oregon. The coalition, including Arizona, Colorado, Connecticut, Delaware, Illinois, Maine, Minnesota, Nevada, New Mexico, New York and Vermont, challenges Trump’s authority to impose tariffs on all imported goods using emergency powers.

The 80-minute session will begin at 10am US Eastern time. The arguments, which exceed the court’s usual 60-minute format, will be split: 40 minutes for the government, 20 each for the private and state petitioners, plus 10-minute rebuttals per side, underscoring the high stakes.

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Canada, Brazil hardest hit as Trump unleashes new global tariff blitz

Canada, Brazil hardest hit as Trump unleashes new global tariff blitz

Trump on Sunday backed away from earlier hints that he might attend the Supreme Court arguments in person, saying he would stay away to avoid becoming a distraction.