Former U.S. President Donald Trump has issued a stern warning to global buyers of Iranian oil, stating that any country or individual purchasing crude or petrochemical products from Iran will face immediate secondary sanctions from the United States.

“They will not be allowed to do business with the United States of America in any way, shape, or form,” Trump declared in a statement posted on Truth Social, as reported by Reuters.

The announcement comes in the wake of postponed nuclear talks between Washington and Tehran, originally set to take place in Rome this Saturday.

A senior Iranian official confirmed to Reuters that a new date would be arranged, “depending on the U.S. approach.”Trump’s administration has recently revived its “maximum pressure” campaign against Iran, reinstating sanctions on several entities.

This includes a crude oil storage terminal based in China and an independent oil refiner accused of facilitating illegal trade.The former president’s strategy aims to reduce Iran’s oil exports to zero and prevent it from advancing its nuclear ambitions.

Secondary sanctions, a powerful U.S. tool, target foreign entities that engage with sanctioned countries by threatening to cut off their access to the American market.

Analysts suggest that for these sanctions to be truly effective, the U.S. would need to target institutions such as Chinese banks, which currently facilitate the bulk of Iranian oil purchases.China remains Iran’s largest crude buyer.