"Reagan was more powerful and smarter than Trump, and he was a better actor in making threats, and he also moved against us and they shot down our plane," Khamenei said in a speech carried on state television.
In 1988, a U.S. warship shot down an Iranian passenger plane over the Gulf, killing all 290 aboard, in an incident which Washington said was a mistake. Tehran said it was a deliberate attack on Iran, then at war with neighbouring Iraq.
"But Reagan is gone and, according to out beliefs, he now faces God's retribution ... while Iran has made great advances in all areas since Reagan's time," Khamenei added.
"This trend will continue under the current American president and any hopes on their part that the Islamic Republic would back off or weaken is futile."
He announced the shift in U.S. policy in a speech in which he detailed a more aggressive approach to Iran over its nuclear and ballistic missile programmes and its support for militant groups in the Middle East.
Under the nuclear deal, sanctions on Iran were lifted in return for Tehran rolling back technologies with nuclear bomb-making potential.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)