Iranian Foreign Minister Mohammad Javad Zarif  Photo: Xinhua

Iran said on Friday it had taken a step to further downgrade its commitments to a 2015 nuclear deal with the world's most powerful nations, according to Iranian media, in retaliation to US sanctions reimposed on Tehran.

Iran said Wednesday it would begin developing centrifuges to speed up the enrichment of uranium, which can produce fuel for power plants or for atomic bombs. Tehran denies seeking nuclear weapons.

"Foreign Minister [Mohammad Javad] Zarif, in a letter to EU policy chief [Federica Mogherini] announced that Iran has lifted all limitations on its [nuclear] Research and Development activities," Iran's Students News Agency (ISNA) quoted Foreign Ministry spokesperson Abbas Mousavi as saying.

Under the deal, Iran is allowed limited research and development on advanced centrifuges, which accelerate the production of fissile material that can be used to make a nuclear bomb. 

Iran also agreed to limitations on specific research and development activities for eight years.

US President Donald Trump pulled the United States out of the deal last year, arguing it did not go far enough, and reimposed sanctions that has slashed Iran's crude oil sales by more than 80 percent.

Iran has responded by scaling back its nuclear commitments since May and has threatened to continue removing restraints on its nuclear program unless European parties to the pact did more to shield Iran's economy from the US penalties.

Britain and France, both parties to the pact, have called on Iran to refrain from any concrete action that does not comply with the agreement.

State TV said Iran's Atomic Energy Organization would unveil on Saturday details of Tehran's new step, which President Hassan Rouhani will accelerate Iran's nuclear program.