"In conclusion, in response to a question about the possibility of diluting 60 percent enriched uranium... the head of the Atomic Energy Organization said that this depends on whether all sanctions would be lifted in return," the official IRNA news agency reported, referring to agency chief Mohammad Eslami, without specifying whether this included all sanctions on Iran or only those imposed by the United States.

Diluting uranium means mixing it with blend material to reduce the enrichment level, so that the final product does not exceed a given enrichment threshold.

Before US and Israeli strikes on its nuclear facilities in June last year, Iran had been enriching uranium to 60 percent, far exceeding the 3.67 percent limit allowed under a now-defunct nuclear agreement reached with world powers in 2015.

Western countries, led by the United States, suspect Tehran is seeking to develop nuclear weapons, a claim denied by Iran.

According to the UN's nuclear watchdog, Iran is the only non-nuclear-weapons state enriching uranium to 60 percent.

It is also unknown where more than 400 kg of highly enriched uranium that Iran possessed prior to the war has ended up, with UN inspectors last recording its location on June 10.

Such a stockpile could allow Iran to build more than nine nuclear bombs if enrichment reached 90 percent.

US President Donald Trump has repeatedly called for Iran to be subject to a total ban on enrichment, a condition unacceptable to Tehran and far less favourable than the 2015 agreement.

Iran maintains it has a right to a civilian nuclear programme under the provisions of the Nuclear Non-Proliferation Treaty, to which it and 190 other countries are signatories.