Iran warned on Monday world powers that it will not offer any further "deadlines" to save the 2015 nuclear deal by September as it threatened to restart deactivated centrifuges and sharply step up its enrichment of uranium to 20 percent purity.
Iranian foreign ministry spokesman Abbas Mousavi told reporters that the last chance for saving the pact will pass after a 60-day deadline.
The previous day, Iranian officials said the country would take further steps toward the "reduction" of its compliance with the accord after the deadline. Iran has already breached the deal's limits on uranium enrichment and stockpiling.
Mousavi said Iran is still open to negotiations with its European partners and expressed hope they would "take steps forward" toward implementing their commitments.
Iran will only discuss issues included in current nuclear deal and not take part in negotiations for a new deal, he added.
Tehran’s third step in reducing commitments under the nuclear deal will be stronger, he warned.
Later, Behrouz Kamalvindi, spokesman for Iran's Atomic Energy Organization, threatened to restart deactivated centrifuges and confirmed an announcement that Tehran had enriched uranium beyond the 3.67% purity that the deal allows, passing 4.5%, according to the student's news agency INSA.
The threats would go far beyond the small steps Iran has taken in the past week to nudge its stocks of fissile material just beyond limits in the nuclear pact.
That could raise serious questions about whether the agreement, intended to block Iran from making a nuclear weapon, is still viable.
Kamalvindi said the authorities were discussing options that included the prospect of enriching uranium to 20% purity or beyond, and restarting centrifuges that were dismantled as one of the deal's core aims.
"There is the 20% option and there are options even higher than that but each in its own place," Kamalvandi said, according to state television. "Restarting IR-2 and IR-2 M centrifuges is an option."
Such threats will put new pressure on European countries, which insist Iran must continue to comply with the agreement even though the United States is no longer doing so.
Iran has breached the 3.67% purity limit of enriched uranium set by its nuclear deal with world powers, confirmed the UN nuclear watchdog on Monday.
“(International Atomic Energy Agency) Director General Yukiya Amano has informed the IAEA Board of Governors that Agency inspectors on 8 July verified that Iran is enriching uranium above 3.67% U-235,” an IAEA spokesman said, referring to the fissile uranium-235 isotope.
Iran’s main demand - in talks with the European parties to the deal and as a precondition to any talks with the United States - is to be allowed to sell its oil at the levels before Washington pulled out of the agreement and restored sanctions.
The confrontation has taken on a military dimension, with Washington blaming Tehran for attacks on oil tankers, and Iran shooting down a US drone, prompting aborted US air strikes.
The Europeans, who object to President Donald Trump’s withdrawal from the deal, have so far failed to salvage the pact by shielding Iran’s economy from US sanctions, which cost billions of dollars in lost oil sales.
Meanwhile, China expressed regret at Iran's decision to boost uranium enrichment, its foreign ministry said on Monday, reiterating that the standoff needed to be resolved diplomatically.
At a daily briefing, ministry spokesman Geng Shuang also reiterated that China called on all sides involved to exercise restraint.
Earlier, Japan voiced serious concern over Iran's decision to increase uranium enrichment, urging it to return to its earlier commitment.
Deputy Chief Cabinet Secretary Yasutoshi Nishimura said Monday that Japan is "seriously concerned and closely watching" the development on the nuclear deal and increased tension in the Middle East.
Nishimura urged Iran to "immediately return to its commitment under the agreement and avoid any further steps that would undermine the nuclear agreement."
Japan's Prime Minister Shinzo Abe visited Tehran for talks with Iranian leaders but did little to help deescalate tensions with the US.