Salehi seeks to placate hardline critics of Geneva nuclear deal by saying new generation of centrifuges is on the way

The head of Iran's atomic energy agency had said the country is building a new generation of centrifuges for uranium enrichment but that they need more tests before being mass-produced, apparently trying to counter internal criticism of its deal with world powers.

Under an agreement made last month in Geneva, Iran promised not to bring new centrifuges into operation for six months, part of temporary limitations on its uranium enrichment programme in return for easing some sanctions. But the deal does not stop it from developing centrifuges.

Ali Akbar Salehi's comments seem to show the country is moving ahead with its nuclear programme to fend off criticism by Iranian hardliners, who have called the deal a surrender to western pressure. The government of Iran's new president, Hassan Rouhani, says the deal recognises Iran's right to enrich uranium.

US and its allies accuse Iran of seeking to build a nuclear weapon. Iran denies the charge, saying its nuclear programme is for peaceful purposes, including power generation and medical treatments. In his comments reported by state TV on Thursday, Salehi did not elaborate on how long the building and testing would take. "The new generation of centrifuges is under development. But all tests should be carried on it before mass production," Salehi was quoted as saying.

He also said Iran has 19,000 centrifuges, though he did not say how many were operational. In August, Iran said it had 18,000 including 1,000 advanced centrifuges. Iran has given the UN nuclear watchdog information on the new generation of machines.

Iran has long said it is developing more sophisticated centrifuges to enrich uranium faster.

Under the Geneva deal, Iran agreed to limit its uranium enrichment to 5% and neutralise its stockpile of 20%-enriched uranium.Uranium can be used to build a weapon if it is enriched to more than 90%. At lower levels, it is used to power nuclear reactors.