Iran's nuclear chief Ali Akbar Salehi said the Islamic republic would halt production of 20 percent enriched uranium by noon (0830 GMT) on Monday, the official IRNA news agency reported.
"Voluntarily halting the production of 20 percent uranium enrichment is the major measure that we are undertaking on Monday by noon," Salehi said, referring to a landmark nuclear deal clinched between Iran and world powers.
"Two cascades (used to enrich uranium) in Natanz and four cascades in Fordo will be disconnected by noon which means the production of 20 percent is practically stopped," Salehi added.
Inspectors from the UN nuclear watchdog arrived in Tehran on Saturday to oversee implementation of the deal that puts temporary curbs on Iran's nuclear programme.
The team is tasked with reporting back to the Vienna-based agency on steps Tehran must take under the deal agreed in November and finalised last week between Iran and the P5+1 group of world powers.
Agreed after years of fruitless negotiations, the accord is to come into effect on January 20 and will last for six months during which Iran -- among other obligations -- must limit its enrichment of uranium to five percent.
The country must also begin to neutralise its stockpile of uranium purified to 20 percent, a few technical steps short of weapons-grade.
"We have enough stockpile of 20 percent uranium enrichment for the next four or five years, therefore there is no need to do that," Salehi added.
In return, Iran will be granted modest relief from Western sanctions and access to nearly $4.2 billion of frozen assets in eight instalments.
Western governments suspect Iran's civil nuclear programme masks a drive for a weapons capability, an allegation Tehran strongly denies.