US President Donald Trump has issued a stern warning to Iran and its trading partners, threatening immediate secondary sanctions on any country or individual that continues to purchase Iranian oil or petrochemical products.

“All purchases of Iranian oil or petrochemical products must stop, NOW! Any country or person who buys ANY AMOUNT will be subject to, immediately, secondary sanctions,” Trump posted on Truth Social. “They will not be allowed to do business with the United States of America in any way, shape, or form.”

The threat comes after the postponement of the fourth round of indirect nuclear talks between Iran and the US, which was scheduled to take place in Rome. The talks, mediated by Oman, were delayed due to “logistical reasons,” according to Omani Foreign Minister Sayyid Badr bin Hamad Al Busaidi.

Iranian Foreign Ministry spokesman Esmaeil Baghaei confirmed the postponement and reiterated Iran’s commitment to diplomacy. “We remain determined to use diplomatic means to secure our legal and legitimate interests and end the sanctions and economic pressure campaign,” he stated.

The Rome round was expected to be a key step forward in efforts to revive negotiations that aim to limit Iran’s nuclear activities in exchange for easing crippling US sanctions. Previous rounds were held in Muscat, Oman, with Iran’s Foreign Minister Abbas Araghchi and US envoy Steve Witkoff leading discussions.

The diplomatic freeze comes at a tense time. Iran’s nuclear stockpile has reached near weapons-grade enrichment levels, raising alarm among US officials. President Trump has repeatedly threatened military action if talks fail.

Meanwhile, tensions continue to rise in the region. The US military is engaged in “Operation Rough Rider” targeting Yemen’s Houthi rebels, whom Washington accuses Iran of arming. “We see your lethal support to the Houthis,” said US Defense Secretary Pete Hegseth in a sharp message directed at Iran. “You were warned. You will pay the consequence at the time and place of our choosing.”

The backdrop to the diplomatic developments also includes a deadly explosion at an Iranian port last Saturday, which killed at least 70 people and injured more than 1,000.

Iran’s oil sector, which averaged 2.9 million barrels of crude production daily in 2023, remains the backbone of its economy. Trump’s warning signals renewed pressure under his “maximum pressure” strategy, a hallmark of his administration since taking office.