Iran’s supreme leader has warned that the United States will suffer “unforgettable lessons” at the hands of Tehran and its regional allies, accusing the US of repeatedly violating the memorandum of understanding (MoU) between the two countries.

A written statement attributed to Mojtaba Khamenei was read out on state television on Saturday, in which the supreme leader said Washington’s breaches of last month’s MoU showed that President Donald Trump’s signature was “utterly worthless and invalid”.

“The repeated breach of agreements by the Great Satan vis-à-vis the accord has once again proven to all that the signature of the President of America is now utterly worthless and invalid, and that bullying, hegemonism and savagery are inseparable components of the American creed and doctrine,” the statement read.

“Now that the American enemy is seeking to foment war and suffer heavier costs and further humiliation, it should know that the dear nation of Iran and the Resistance Front hold unforgettable lessons for it,” it added.

The US dramatically escalated its attacks on Iran this week by targeting civilian infrastructure, including bridges, railway lines and water desalination plants.

Tehran has responded by successfully striking civilian infrastructure in Kuwait, with authorities there urging everyone to ration electricity.

The US-Israeli war on Iran, which began in February, is seen as existential by the country’s senior leadership.

Tehran has shown no sign of caving to the increasing demands from the Trump administration, as regional countries continue to push for an end to the conflict behind the scenes.

Khamenei said the US has “revealed its true face,” exposing its “deceitfulness, irrationality, unreliability and wickedness”.

He called on Iranians to trust the leadership to protect the country, urging people to remain “vigilant” and “active” as the fighting grinds on.

Reports have surfaced in recent days that the Houthis in Yemen could close the Bab al-Mandeb gateway to the Red Sea in support of their crucial ally Iran. That would further destabilise global energy markets, increase inflation and apply additional pressure on Trump to halt attacks.

The war is deeply unpopular in the US and has inflicted economic harm on Americans.

The MoU mediated by Qatar and Pakistan and signed last month aimed to create the conditions to bring the war to a permanent end.

However, Tehran and Washington have since declared the accord “over” after accusing each other of violating it. (AP)