Iran's Ambassador to the Vienna-based international organizations Kazem Gharibabadi says that change in method of enriching 60-percent uranium is based on a pre-scheduled plan.

Gharibabadi made the remarks on Thursday while speaking about the fresh report released by the International Atomic Energy Agency (IAEA) about Iran's nuclear activities in Natanz site, center of Iran.

The change was not a new issue, said he, adding that it is completely related to technical decisions and measures.

Such a change was also predicted at design information questionnaire presented by Iran to the IAEA last week, the ambassador noted.

IAEA has verified through a report that IR-4 machines  enrich to up to 20 percent, and IR-6 are used to enrich to up to 60 percent.