"EU statement today is why JCPOA is where it is: the US has bullied Europe-and rest of world-for a year and EU can only express 'regret'," Zarif tweeted in response to the European Union rejecting Tehran's threat to resume nuclear work.

"Instead of demanding that Iran unilaterally abide by a multilateral accord, EU should uphold obligations - including normalisation of economic ties."

The JCPOA, or Joint Comprehensive Plan of Action, is the landmark 2015 deal between Iran and world powers including the EU and the United States which offered sanctions relief to the Islamic republic for scaling back its nuclear program.

In May 2018 President Donald Trump withdrew the US from the deal and reinstated unilateral economic sanctions.

On Wednesday Iran's President Hassan Rouhani said Iran would no longer implement some parts of the deal and threatened to go further if the remaining sides of the pact failed to deliver sanctions relief to counterbalance Trump's renewed assault on the Iranian economy within 60 days.

EU diplomatic chief Federica Mogherini and France, Germany and Britain -- the three European signatories to the deal -- on Thursday denounced Iran's threat to restart nuclear work but vowed to save the deal.

"We strongly urge Iran to continue to implement its commitments under the JCPOA in full as it has done until now and to refrain from any escalatory steps," they said in a joint statement.

"We reject any ultimatums and we will assess Iran's compliance on the basis of Iran's performance regarding its nuclear-related commitments under the JCPOA."