Iran's nuclear chief Ali Akbar Salehi has said the country is building a new generation of centrifuges for uranium enrichment, but that they need more tests before being mass-produced.
Salehi is apparently seeking to counter internal criticism of its deal with the world powers reached last month in Geneva, the Guardian reports.
Under the interim deal, Iran promised not to bring new centrifuges into operation for six months, and get relief from some of the international sanctions in return.
However, the deal does not stop it from developing centrifuges, the report added.
Iranian hardliners have repeatedly criticized the deal as surrender to western pressure.