Behrouz Kamalvandi, the spokesman of the Atomic Energy Organization of Iran, said technical preparations for the new level of enrichment have been completed and enrichment over 3.67% will begin "within a few hours", ISNA reported.
He made the remarks during a joint press conference with Deputy Foreign Minister Abbas Araqchi and Government Spokesman Ali Rabiei.
The announcement comes at a time of sharply increased US-Iran tensions, a year after Washington quit the pact and reimposed sanctions that had been lifted under the accord in exchange for Tehran curbing its nuclear work, Financial Tribune reported.
On May 8, Iran said it would no longer respect the limits set on its stockpiles of enriched uranium and heavy water, adding that it would abandon further nuclear commitments, including exceeding the agreed uranium enrichment from July 7.
The phased measures are part of an effort to press the European signatories—namely France, Britain, and Germany—to salvage the pact by protecting Iran's economic interests from US sanctions.
Europe had pleaded with Iran to keep within its parameters, pledging that it would work to offset the US exit.
"Today, the 60-day deadline given to Europe ended," Kamalvandi said, adding that Tehran is fully prepared to enrich uranium "with any speed, at any level and with any amount".
Before the deal known as the Joint Comprehensive Plan of Action was sealed, Iran produced 20% enriched uranium needed to fuel its Tehran reactor and the level of enrichment for its southern Bushehr Nuclear Power Plant was 5%.
The spokesman said enriching uranium for fueling the Tehran reactor is not currently on Iran's agenda.
"Reversible" Measures
In a tweet on Sunday, Foreign Minister Mohammad Javad Zarif said, "We reserve the right to continue to exercise legal remedies within JCPOA to protect our interests in the face of US #EconomicTerrorism. All such steps are reversible only through E3 compliance.
"Having failed to implement their obligations under JCPOA—incl after US withdrawal—EU/E3 should at minimum politically support Iran's remedial measures under Para 36, incl at IAEA. E3 have no pretexts to avoid a firm political stance to preserve JCPOA & counter US unilateralism."
Zarif was referring to a clause that provides a mechanism to resolve disputes when parties believe other signatories are not fulfilling their obligations.
The United States has called an emergency meeting of the International Atomic Energy Agency's 35-nation Board of Governors to discuss Iran. The meeting will be held on July 10.
Senior nuclear negotiator, Araqchi, told reporters that the new measures are being taken because Iran's demands have not been met, adding that the country would further reduce its nuclear commitments if Europe fails to uphold its side of the deal within the next 60 days.
“The next planned steps will be announced in due course and the remaining parties can use the time available to find solutions,” the deputy foreign minister was quoted as saying by ISNA.
"Rolling back our commitments is in line with saving JCPOA, not killing it," said.
He reiterated that the plans announced by Tehran are based on the legal mechanisms stipulated in the agreement and "are not a breach of the JCPOA in our view".
Araqchi said the new EU-Iran trade mechanism forms a "good basis" for trade between the two sides, but substantial credit facilities are needed for it to be beneficial.
France, Britain and Germany have set up a special trade channel known as INSTEX or the Instrument in Support of Trade Exchanges, which aims to circumvent US sanctions.
But the arrangement is currently confined solely to easing trade in humanitarian goods that are not subject to US sanctions, such as food and medicine, not oil.
The senior diplomat said Iran will use every means to improve economic conditions, but "has not pinned its hopes on INSTEX".
US Participation in Talks
The deputy foreign minister said US officials can attend ongoing negotiations between Iran and the remaining parties to the deal provided Washington "lifts sanctions", beginning with "oil and banking sanctions".
Araqchi ruled out the possibility of renegotiating the nuclear deal, adding that "it should be implemented without a single word being added to or removed from it".
IAEA said on Sunday its inspectors, who are in Iran and will report back after inspecting Tehran’s uranium enrichment level.
"We are aware of Iran's announcement related to its uranium enrichment level," a spokesman for the UN nuclear watchdog said, Reuters reported.
"IAEA inspectors in Iran will report to our headquarters as soon as they verify the announced development," the official added.