President Donald Trump has announced a raise in the global tariff rate from 10 to 15 per cent, a day after the U.S. Supreme Court struck down his sweeping tariff as unlawful.

‎Mr Trump announced this on his Truth Social handle on Saturday.

‎He said, “Please let this statement serve to represent that I, as president of the United States of America, will be, effective immediately, raising the 10 per cent worldwide tariff on countries, many of which have been ‘ripping’ the U.S. off for decades, without retribution (until I came along!), to the fully allowed and legally tested 15 per cent level.”

‎Mr Trump’s decision to raise the global tariff rate followed a 6-3 ruling by the Supreme Court on Friday, which held that the U.S. president exceeded his authority under the International Emergency Economic Powers Act (IEEPA) by imposing broad tariffs without explicit congressional approval.

Despite the ruling on Friday, Mr Trump proceeded to make the announcement, describing the court’s decision as “poorly written and extraordinarily anti-American.

‎The 79-year-old businessman hinged the basis of his decision on Section 122 of the Trade Act of 1974, which permits a temporal maximum of 15 per cent under alternative legal provision.

According to the Trade Act, tariffs of up to 15 per cent can be imposed on imports for up to 150 days to address trade imbalances, after which Congress would need to act to extend or authorise further measures.

‎Mr Trump’s decision to raise import tariffs could heighten international trade tensions in coming days, as prices of imported goods could soar higher.