WASHINGTON – Iran has begun taking its uranium enriching centrifuges off-line, a key step toward implementation of the nuclear accord reached in July with world powers, the country’s atomic energy chief said.Signatories of the agreement are working toward a day of implementation, to be declared once Iran completes a specific set of tasks. Those steps include neutering its plutonium reactor, reducing its nuclear enrichment capacity and stockpile, and increasing access and transparency at its declared nuclear facilities.As soon as Iran completes all these steps – a process the Obama administration believes will take from four to six months – the deal will be formally implemented, and Iran will begin receiving sanctions relief.“We have already started to take our measures vis-a-vis the removal of the centrifuge machines – the extra centrifuge machines. We hope in two months time we are able to exhaust our commitment,” Ali Akbar Salehi said during a visit to Tokyo.In a separate development that appeared to confirm that Iran had begun implementing its side of the deal, 20 hardline conservative members of Iran’s parliament wrote to President Hassan Rouhani to complain about the deactivation of centrifuges in two enrichment plants at Natanz and Fordow.“Unfortunately in the last two days some contractors entered Fordow and started dismantling centrifuges...they said they could finish the job in two weeks,” Fars News Agency cited the lawmakers, among those loath to accept the nuclear deal, as saying.Iran’s government would like to see the deal implemented, and sanctions lifted, by February, when Iranians will go to the polls for parliamentary elections. American officials say that target is ambitious, and note that sanctions cannot be relieved until the International Atomic Energy Agency – the UN body tasked with policing the deal – can verify the completion of these key initial obligations.Nevertheless, all parties to the agreement are operating based on the assumption that Iran will fully comply in due course.US President Barack Obama has directed his cabinet to prepare for an eventual day of implementation, and European governments are broadening ties with the Islamic government.According to Interfax, a Moscow news agency, Russian state-owned arms company Rosoboronexport said on Monday it is preparing a contract to supply Iran with S-300 missile systems. The technology will significantly upgrade Iran’s anti-aircraft and anti-ballistic missile capabilities.Reuters contributed to this report.