The US Supreme Court is set to hear arguments on the legality of Donald Trump's unprecedented use of powers for sweeping global tariffs in a case striking at the heart of the president's economic agenda.
Since returning to the White House, Mr Trump has invoked emergency economic powers to impose "reciprocal" tariffs over trade practices the US deemed unfair, alongside separate duties targeting his country's biggest trading partners: Mexico, Canada and China.
However, these tariffs, a key prong of his "America First" trade policy aimed at protecting and boosting US industries, swiftly faced legal challenges.
A lower court ruled in May that Mr Trump exceeded his authority in imposing the duties, although the administration's appeal allowed them to temporarily stay in place.
The US Court of Appeals for the Federal Circuit ruled 7-4 in August that the levies were illegal - affirming the lower court's finding - prompting Mr Trump to take the fight to the Supreme Court.
The top court's decision will have major ramifications, but this could take months.
The conservative-majority Supreme Court could find the tariffs illegal, blocking duties imposed on goods from countries worldwide.
However, judges could affirm Mr Trump's actions, opening the door to further levies.
Also at stake are billions of dollars in customs revenue already collected and Mr Trump's efforts to leverage tariffs for favorable trade deals - or other political priorities.
The Supreme Court's ruling, however, would not directly affect sector-specific tariffs Mr Trump imposed, including on steel, aluminum and automobiles.
Read more: Why damage from US tariffs may not be as bad as feared
