Iran’s Supreme Leader Mojtaba Khamenei vowed on Saturday to teach the United States “unforgettable lessons,” as renewed hostilities flared following the collapse of a ceasefire agreement between the two countries.

In a written statement carried by state TV, Khamenei said Washington’s continued attacks, despite the existence of a framework deal to end the war, showed that President Donald Trump’s signature was “utterly worthless and devoid of credibility.”

“Now that the American enemy seeks to incite war and bear its most serious consequences, it should know that the dear Iranian nation and the axis of resistance have unforgettable lessons to offer it,” he said.

He added that the US had “once again demonstrated to everyone the worthlessness of the American president’s signature.”

The statement came as Washington and Tehran exchanged strikes after a ceasefire agreement fell apart last week, raising fears of a return to all-out war between the two sides.

Khamenei warned that the Iranian nation and what he called the “resistance front” had further “unforgettable lessons” in store for the United States.