The EU has been the go-between in the indirect talks as Iran refused to negotiate directly with the US since Donald Trump unilaterally withdrew the country from the accord.
Iran said Tuesday it submitted a “written response” to what has been described as a final roadmap to restore its tattered nuclear deal with world powers.
Nabila Massrali, a spokesperson for the European Union on foreign affairs and security policy, said the EU received Iran's response on Monday night.
"We are studying it and are consulting with the other JCPOA participants and the US on the way ahead," she said, using an acronym for the formal name for the nuclear deal, the Joint Comprehensive Plan of Action.
The EU has been the go-between in the indirect talks as Iran refused to negotiate directly with America since then-President Donald Trump unilaterally withdrew the US from the accord in 2018.
As of the last public count, Iran has a stockpile of some 3,800 kilogrammes of enriched uranium.
Under the deal, Tehran could enrich uranium to 3.67% purity, while maintaining a stockpile of uranium of 300 kilogrammes under constant scrutiny of surveillance cameras and international inspectors.
Iran now enriches uranium up to 60% purity — a level it never reached before and one that is a short, technical step away from 90%.
Nonproliferation experts warn Iran now has enough 60%-enriched uranium to reprocess into fuel for at least one nuclear bomb.
Meanwhile, the surveillance cameras have been turned off and other footage has been seized by Iran.
Tehran insists its programme is peaceful.