Iranian Supreme Leader Ayatollah Ali Khamenei on Wednesday declared that Tehran would stick to the 2015 nuclear deal as long as the other signatories respected it, but would "shred" the agreement if Washington pulled out.
Khamenei's comments, quoted by Reuters, came five days after U.S. President Donald Trump adopted a harsh new approach to Iran by refusing to certify its compliance with the deal.
On Monday, Trump said that the complete cancellation of the 2015 deal was a "real possibility."
"I don't want to waste my time on answering the rants and whoppers of the brute president," the Supreme Leader said in a speech to students in Tehran.
"Trump's stupidity should not distract us from America's deceitfulness ... If the U.S. 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," he declared.
Trump's move has put Washington at odds with other parties to the accord - Britain, France, Germany, Russia, China and the European Union - who continue to support the deal.
Khamenei, who has the final say on Iran's state matters, welcomed European support but said it was not sufficient.
"European states stressed their backing for the deal and condemned Trump ... We welcomed this, but it is not enough to ask Trump not to rip up the agreement. Europe needs to stand against practical measures (taken) by America," he stressed, according to Reuters.
"Americans are angry because the Islamic Republic of Iran has managed to thwart their plots in Lebanon, Syria, Iraq and other countries in the region," Khamenei claimed.
Iranian leaders have stepped up their rhetoric in recent days and weeks as it became clearer that Trump was planning not to recertify the deal.
Iran's Foreign Minister, Mohammad Javad Zarif, warned Trump this week of a "reciprocal measure" if sanctions were reimposed on his country.
Iranian President Hassan Rouhani also criticized Trump's speech and vowed to expand Iran's ballistic missile program.
Speaking on Iranian television, Rouhani dismissed Trump's “insults and fake accusations", and said that Iran would stick to the nuclear agreement as long as it was beneficial.