Iranian Foreign Minister Mohammad Javad Zarif in a message advised Europeans to abide by regulations, saying then Iran will reverse.
"Our response to US #EconomicTerrorism & blackmail is opposite of what @realDonaldTrump was led to believe," Zarif wrote on his Twitter account.
He added: "Our 4th step to suspend a #JCPOA provision is foreseen in Para 36 as remedy to US+E3 violations."
"Easy solution for E3/EU: Abide by your obligations & we'll reverse course," Iranian top diplomat said.
Earlier, Iranian Ambassador to London Hamid Baeidinejad said ""Iran, in its 4th step of reducing its commitments, will feed the centrifuges at the Fordow facility with gas."
"This measure would be implemented under the IAEA monitoring and would be reversible if other parties decide to implement their shares of commitments under the nuclear deal," he added.
President Hassan Rouhani announced Iran will take the fourth step of reducing commitments to the JCPOA as of November 6.
Iran's 4th step like the three previous ones will be revocable if it sees other parties comply with the deal, the President said.
Meanwhile, Rouhani noted, Iran states that the country's new activities will be under supervision of the International Atomic Energy Agency (IAEA).