A spokesman for Iran's atomic energy agency said preparations would be made to increase the pace of uranium enrichment even further if the JCPOA collapses.
Tehran's other partners in the deal - Germany, France, Britain, Russia and China - have all condemned Washington's unilateral withdrawal and said they would still live up to their commitments as part of the deal.
German Foreign Minister Heiko Maas huddled with his Chinese counterpart Wang Yi on Thursday and insisted that Berlin "wants to maintain the nuclear agreement and make sure Iran maintains it too".
"However, at this particularly critical juncture, they will not contribute to build confidence in the nature of the Iranian nuclear program".
As European states and China reiterated their commitment to the nuclear deal, Iran's foreign ministry stated that in spite of Washington's move, Tehran would abide by its obligations under the deal, calling on the global community to stand up against "US law-breaking behavior, bullying and disregard for the rule of law". "Yesterday he explained how he would do it - with an unlimited enrichment of uranium to produce an arsenal of nuclear bombs".
"The leader [Ayatollah Khamenei] meant that we should accelerate some process. linked to our nuclear work capacity to move forward faster in case needed", he added, as quoted by Reuters news agency.
The three European powers are scrambling to save the deal - under which Iran curbed its nuclear programme in return for a lifting of worldwide sanctions - as they regard it as the best chance to stop Tehran developing an atomic bomb.
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The statement accused the detainees of "coordinated activity undermining the security and stability of the kingdom". They say the activists feared changes would stop if they did not continue to work for greater rights.
Netanyahu has been a staunch opponent of the Iranian nuclear deal and has repeatedly called for it to be scrapped and for a return of sanctions.
Israeli Prime Minister Benjamin Netanyahu speaks during a joint press conference with French President Emmanuel Macron (not pictured) at the Elysee Palace in Paris, France, June 5, 2018.
"The Iranian nation will not tolerate to be under both sanctions and nuclear restrictions".
US President Donald Trump pulled out last month from the 2015 accord between Iran and world powers that lifted sanctions on Tehran in exchange for curbs to its nuclear program.
The supreme leader said that if the three countries were unable to meet these demands, Iran would resume its enrichment of uranium.
European signatories of the accord back the deal but have concerns over Iran's ballistic missile program and its political influence in the Middle East. Iran says the two issues are non-negotiable.
Katz noted that many global companies from France, England, Germany, Russia and other countries have already announced their intention to suspend their activity in Iran "because they don't want to be subject to the American sanctions".
A European source told AFP that the Iranian enrichment announcement is being interpreted as a bid to step up the pressure on Brussels to deliver on these promises.