TEHRAN, Jan. 14 (Xinhua) -- Kazem Gharibabadi, Iran's ambassador and permanent representative to the Vienna-based international organizations, said that the Islamic Republic has started research and development to upgrade fuel for its Tehran Research Reactor, Iranian Tasnim News Agency reported on Thursday.

Gharibabadi said on Wednesday that the International Atomic Energy Agency (IAEA) released a report informing member states of the agency that Iran has started upgrading fuel for the Tehran Research Reactor.

Iran's ambassador also said that the activity is going to be carried out in three phases in the first stage of which metal uranium will be produced using natural uranium.

Iran informed the international agency of all these stages and Tehran will continue this process, Gharibabadi said, adding that the IAEA inspectors visited the fuel plate production plant several days ago.

Iran launched 20-percent uranium enrichment process on Jan. 4 as part of Iran's Strategic Action Plan to Counter Sanctions which was approved by the parliament in December 2020.

In response to the U.S. withdrawal from the nuclear deal in 2018 and re-imposition of sanctions, Iran has stopped implementing parts of its obligations under the deal.