Iran is set to break the uranium stockpile limit set by Tehran's nuclear deal with world powers in the next 10 days, the country's atomic agency said.
Spokesman Behrouz Kamalvandi said Iran needed to increase uranium enrichment levels up to 20% - only one step away from weapons-grade material.
He spoke during a news conference at the Arak heavy water facility which was broadcast live on Iranian state television.
Mr Kamalvandi's comments follow suspected attacks on oil tankers last week in the region which the US has blamed on Iran.
Tensions between Tehran and Washington are running high, a year after US president Donald Trump unilaterally withdrew America from the 2015 nuclear deal partly brokered by his predecessor, Barack Obama.
Mr Kamalvandi said Iran needs 5% enrichment for its nuclear power plant in the southern port of Bushehr, and 20% enrichment for a Tehran research reactor.
When uranium is mined, it typically has about 140 atoms of an unwanted isotope, U-238, for every atom of U-235.
Refining it to a purity of 3.67%, the level now allowed by the nuclear deal, means removing 114 unwanted atoms of U-238 for every atom of U-235.
The spokesman noted that boosting its purity to 20% means removing 22 more unwanted isotopes per atom of U-235, while going from there to 90% purity means removing just four more isotopes per atom of U-235.
Ninety per cent purity is considered weapons-grade material.
This means that going from 20% to 90% enrichment is a relatively quicker process, something that worries nuclear non-proliferation experts.
Mr Kamalvandi acknowledged that Iran has already quadrupled its production of low-enriched uranium.