Iran will boost its uranium enrichment after July 7 to whatever levels it needs beyond the cap set in the landmark 2015 nuclear deal, President Hassan Rouhani said on Wednesday, defying US efforts to force Tehran to renegotiate the pact.
Iran announced this week it has stockpiled more low-enriched uranium than is permitted under the accord, a move that prompted President Donald Trump - who withdrew the US from the deal last year - to warn Iran was "playing with fire".
"Our level of enrichment will no longer be 3.67. We will put this commitment aside by whatever amount we feel like, by whatever amount is our necessity, our need. We will take this above 3.67," said Rouhani, according to IRIB news agency.
Uranium refined to a fissile purity of 3.67 percent is deemed suitable for electricity generation and is the maximum allowed by the deal. Enrichment to 90 percent yields bomb-grade material.
An increasing stockpile and higher enrichment close the estimated one-year window Iran would need to produce enough material for a nuclear bomb, something Iran denies it wants but the nuclear deal sought to prevent.
European co-signatories said on Tuesday they were "extremely concerned" by Tehran's apparent breach of the deal while Israel said it was preparing for possible involvement in any military confrontation between Iran and the United States.
Rouhani said that if the other signatories do not protect trade with Iran promised under the deal but blocked by Trump's reimposition of tough sanctions, Iran would start to revive its Arak heavy-water reactor after July 7.
As required by the accord, Iran said in January 2016 that it had removed the core of the reactor and filled it with cement.
"From (July 7) onward with the Arak reactor, if you don't operate (according to) the programme and time frame of all the commitments you've given us, we will return the Arak reactor to its previous condition," said Rouhani.
"Meaning, the condition that you say is dangerous and can produce plutonium," he said, referring to a key ingredient in a nuclear weapon. "We will return to that unless you take action regarding all your commitments regarding Arak."
The US rushed an aircraft carrier, B-52 bombers and F-22 fighters to the region and Iran recently shot down a US military surveillance drone, claiming a violation of territory.
On Wednesday, Iran marked the US Navy's downing of an Iranian passenger jet in 1988, an incident that killed 290 people.
Speaking at a Cabinet meeting in Tehran, Rouhani's comments seemed to signal that Europe has yet to offer Iran anything to alleviate the pain of the renewed US sanctions targeting its oil industry and top officials.
"Our advice to Europe and the United States is to go back to logic and to the negotiating table," Rouhani added.
"Go back to understanding, to respecting the law and resolutions of the UN Security Council. Under those conditions, all of us can abide by the nuclear deal."
Both Iran and the UN's nuclear watchdog agency confirmed on Monday that Tehran had breached that limit.
While that represents Iran's first major departure from the accord, it still remains likely a year away from having enough material for a nuclear weapon.
Iran insists its programme is for peaceful purposes, but the West fears it could allow Iran to build a bomb.
Mourning 1988's victims
On Wednesday, relatives of those 290 people killed in the 1988 downing of the Iranian passenger jet threw flowers into the Strait of Hormuz in mourning.
The downing of Iran Air flight 655 by the US Navy remains one of the moments the Iranian government points to in its decades-long distrust of America.
They rank it alongside the 1953 CIA-backed coup that toppled Iran's elected prime minister and secured Shah Mohammad Reza Pahlavi's absolute power until he abdicated the throne before the 1979 Islamic Revolution.
Iranian state television aired footage on Wednesday of mourners in the strait, as armed Iranian Revolutionary Guard fast boats patrolled around them.