"The continuation of these illegal behaviours will not change Iran's logical, legitimate and international law-based positions," a foreign ministry statement said, condemning what it called "pressure on Iran's trade and economic partners".

It added that such sanctions have created "deep suspicion and mistrust about the seriousness of America on the path of diplomacy".

On Thursday, Trump vowed to enforce sanctions and called for a global boycott of "any amount" of Iranian oil or petrochemicals.

"All purchases of Iranian Oil, or Petrochemical products, must stop, NOW!" Trump wrote on his Truth Social platform.

"Any Country or person who buys ANY AMOUNT of OIL or PETROCHEMICALS from Iran will be subject to, immediately, Secondary Sanctions," he added.

His remarks came after Iran said a fourth round of nuclear talks with the United States, in Rome on Saturday, has been postponed, with mediator Oman citing "logistical reasons" for the delay.

Oman said the date for a new round "will be announced when mutually agreed".

Tehran and Washington have held three rounds of talks since April 12, the highest-level contact on Iran's nuclear programme since Trump abandoned a nuclear accord with world powers in 2018.

The talks were held after Trump wrote to Iran's supreme leader Ayatollah Ali Khamenei in March urging negotiations but warning of potential military action if diplomacy failed.

Since returning to office in January, Trump has revived the "maximum pressure" policy of sanctions against Iran, with the latest announced on Wednesday and targeting seven companies accused of transporting Iranian-origin petroleum products.

Tensions over Iran's nuclear programme soared after Washington withdrew from the 2015 deal with world powers which offered Tehran sanctions relief in return for curbs on its nuclear ambitions.

Iran adhered to the agreement for a year afterwards before beginning to roll back its compliance.

Western countries have since accused Tehran of seeking atomic weapons, an allegation it has consistently denied, insisting that its nuclear programme is for peaceful civilian purposes only.