U.S. President Donald Trump restarted blackmail against Iran on Thursday, saying any country or person that buys oil or petrochemicals from Iran would face immediate U.S. sanctions, after the indirect talks between the two countries were postponed.

"All purchases of Iranian Oil, or Petrochemical products, must stop, NOW! Any Country or person who buys ANY AMOUNT of OIL or PETROCHEMICALS from Iran will be subject to, immediately, Secondary Sanctions," Trump wrote on Truth Social.

"They will not be allowed to do business with the United States of America in any way, shape, or form. Thank you for your attention to this matter," he added.

Trump implemented what he calls a "maximum pressure" campaign against Iran since taking office in January, including tougher sanctions on oil exports and threats of military action.

Trump's comments came after Iranian Foreign Ministry spokesman Esmaeil Baghaei said on Thursday that the fourth round of indirect nuclear talks between Iran and the United States, scheduled for Saturday in Rome, had been postponed at the mediator Oman's proposal.

Baghaei reaffirmed Iran's determination to use diplomacy to safeguard the nation's "legitimate and legal" interests and to end the sanctions and economic pressure against Iran.

Earlier in the day, Omani Foreign Minister Sayyid Badr bin Hamad Al Busaidi announced on social media platform X that the fourth round of the Iran-U.S. talks scheduled for Saturday had been postponed for "logistical reasons," adding, "New dates will be announced when mutually agreed."