It comes after the UN's watchdog confirmed Tehran has started the process of enriching uranium to 20 percent. The EU said it marks "a significant departure from Iran's nuclear commitments" under the pact.
The European Union vowed on Tuesday to save the Iran nuclear deal after the UN's watchdog confirmed Tehran has started the process of enriching uranium to 20 percent.
European Commission spokesman Peter Stano said the steps taken by Iran were of "deep concern" and that they represent "a significant departure from Iran's nuclear commitments" under the pact.
But he also insisted that "the strict verification and transparency measures remain in place" under the deal.
"We will redouble our efforts to preserve the agreement and return to its full implementation by all parties," Stano said.
It follows an announcement by the Iranian government on Monday that the country had started enriching uranium of up to 20% at its underground Fordo nuclear facility.
It would put Tehran's program a technical step away from weapons-grade levels,
"A few minutes ago, the process of producing 20% enriched uranium has started in Fordo enrichment complex," government spokesman Ali Rabeie told Iranian state media.
The developments come amid heightened tensions between Iran and the US in the waning days of the administration of President Donald Trump.
The deal’s main aim was to extend the time Iran would need to produce enough fissile material for a nuclear bomb, if it chose to, to at least a year from roughly two to three months. It also lifted international sanctions against Tehran.
On January 1, the International Atomic Energy Agency (IAEA) said Tehran had told the watchdog it planned to resume enrichment up to 20% at Fordo site, which is buried inside a mountain.
Government spokesman Ali Rabeie said the process had now started "after taking measures like informing the UN nuclear watchdog."
Confirmation came hours later from the IAEA, which said a total of 1,044 IR-1 centrifuges were being used.
"Iran today began feeding uranium already enriched up to 4.1% U-235 into six centrifuge cascades at the Fordow Fuel Enrichment Plant for further enrichment up to 20%," said the agency.
IAEA inspectors present at the site had seen a cylinder with "feed material" being connected to the cascade "to start the production of uranium up to 20%," it said.
Iran’s decision to begin enriching to 20% a decade ago nearly brought an Israeli strike targeting its nuclear facilities, tensions that only abated with the 2015 nuclear deal.
Israeli PM Benjamin Netanyahu, a long-time critic of the accord, hit out at "Iran's decision to continue violating its commitments."
"(It) can be explained in no other way than the further realization of its intention to develop a military nuclear program," he said in a statement released by his office.
Iran has always insisted its program is peaceful.