Khamenei threatens to 'shred' nuclear deal if US quits
Khamenei also dismissed US President Donald Trump's aggressive criticism of the deal, calling his comments from last Friday "rants and whoppers".
"I don't want to waste my time on answering the rants and whoppers of the brute US president," Khamenei said in a speech to students in Tehran, published on his Telegram channel.
"Trump's stupidity should not distract us from America's deceitfulness ... If the US tears up the deal, we will shred it ... Everyone should know that once again America will receive a slap in its mouth and will be defeated by Iranians."
Khamenei said Iran would stick by its commitments under the 2015 nuclear deal, which Trump has threatened to "terminate" unless the US Congress tightens sanctions on the country.
"They are angry as today the Islamic republic of Iran has disrupted their plans in Lebanon, Syria and Iraq," Khamenei said.
"Everyone be assured that this time, too, America will be slapped and defeated by the nation of Iran."
Khamenei said the world should not be fooled by Trump's public persona.
"The US president displays stupidity, but this should not cause us to ignore America's mischief," he said.
Khamenei's comments were the first response five days after Trump's threatened to terminate the nuclear deal and called for tougher sanctions on Iran over "destabilising activities" in the Middle East.