"Tehran has started different steps to reduce its peaceful nuclear commitments in order to maintain and balance its commitments under the JCPOA and if the Europeans fail to fulfil their obligations, we will take the fifth step," Press TV quoted Secretary of Iran's Supreme National Security Council Ali Shamkhani as saying on Sunday.
US President Donald Trump, a stern critic of the historic deal, unilaterally pulled Washington out of the Joint Comprehensive Plan of Action in May 2018, and unleashed the "toughest ever" sanctions against the Islamic Republic.
In response to the US unilateral move, Tehran has so far rowed back on its nuclear commitments four times in compliance with Articles 26 and 36 of the JCPOA, but stressed that its retaliatory measures will be reversible as soon as Europe finds practical ways to shield the mutual trade from the US sanctions.
As a first step, Iran increased its enriched uranium stockpile to beyond the 300 kilograms set by the JCPOA.
In the second step, Tehran began enriching uranium to purity rates beyond the JCPOA limit of 3.76 per cent.
In the third phase, after the Europeans failed to meet a 60-day deadline to meet Iran's demands and fulfil their commitments under the deal, Iran started up advanced centrifuges to boost the country's stockpile of enriched uranium and activated 20 IR-4 and 20 IR-6 centrifuges for research and development purposes.
In November, Iran began injecting gas into centrifuges at the Fordow plant as part of its fourth step away from the JCPOA under the supervision of the IAEA.
Shamkhani said that after the US pullout, the three European parties to the deal vowed to guarantee Iran's economic interests in accordance with the JCPOA and to keep the deal alive, but they have so far failed to implement practical measures to save the agreement.
"It was the US President Donald Trump who started to reduce the JCPOA commitments by exiting the JCPOA and after that, Europe completed the US measures by ignoring its JCPOA commitments," the official added.
( With inputs from IANS )