The Secretary of Iran's Supreme National Security Council said on Tuesday that the Islamic Republic will take new steps to reduce its commitments under its nuclear deal with world powers on July 7.
Iran will speed up enrichment of uranium after a deadline given to European countries to prevent this ends on Thursday, the spokesman for Iran's Atomic Energy Organisation said on Wednesday, according to the IRIB news agency.
"The deadline of the Atomic Energy Organisation for passing the production of enriched uranium from the 300 kilogram border will end tomorrow," the organisation's spokesman Behrouz Kamalvandi said.
"With the end of this deadline, the speed of enrichment will speed up."
Tensions between Iran and the United States have escalated ever since, with Washington bolstering its military presence in the region and blacklisting Iran's Revolutionary Guards as a terrorist organisation.
The US has also blamed Iran for last week's attacks on two tankers in the Gulf of Oman, a charge Tehran has denied as "baseless".
Iran has threatened to go even further in scaling down nuclear commitments by July 8 unless remaining partners to the deal -- Britain, China, France, Germany and Russia -- help it circumvent US sanctions and especially enable it to sell its oil.
Watch: Iran hits back after fresh US sanctions, calls it 'permanent closure' of diplomacy
Under the agreement, Iran pledged to reduce its nuclear capacities for several years and allow international inspectors inside the country to monitor its activities in return for relief from international sanctions.
The deal set a limit on the number of uranium-enriching centrifuges, and restricted its right to enrich uranium to no higher than 3.67 per cent, well below weapons-grade levels of around 90 per cent.
It also called on Iran to export enriched uranium and heavy water to ensure that the country's reserves would stay within the production ceiling set by the agreement, yet recent US restrictions have made such exports virtually impossible.