VIENNA — Uranium particles of man-made origin have been discovered at a site in Iran not declared to the United Nations, the U.N. atomic watchdog agency said Monday as it confirmed a litany of violations by Tehran of the 2015 nuclear deal.

The International Atomic Energy Agency said Iran has begun enriching uranium at a heavily fortified installation inside a mountain, is increasing its stockpile of processed uranium, and is exceeding the allowable enrichment levels.

All such steps are prohibited under the agreement Iran reached with world powers to prevent it from building a bomb.

Iran maintains its nuclear program is for peaceful purposes.

But since the U.S. under President Trump pulled out of the pact last year and imposed new sanctions, Iran has been openly stepping up violations in an attempt to pressure the other major signatories – Britain, France, Germany, China and Russia – to help it economically by such means as facilitating the sale of Iranian oil.

The IAEA report came as European Union members met to decide how to keep the deal alive.

“We now need to make it clear to Iran that it can’t continue like this,” German Foreign Minister Heiko Maas told reporters.

Those efforts became more complicated after the IAEA reported that its inspectors confirmed traces of uranium “at a location in Iran not declared to the agency.” The assertion appeared to confirm allegations made by the U.S. and Israel of a secret nuclear warehouse.

The IAEA did not identify the site in the confidential quarterly report, which was distributed to member states and seen by the Associated Press.

In its report, the IAEA also confirmed that the centrifuges are at work at Iran’s Fordo facility – an underground site ringed by anti-aircraft guns — and that enrichment of uranium has been going on there since Saturday.

The nuclear deal had called for Fordo to become a research center. It is now home to more than 1,000 centrifuges.

Also, the agency said Iran continues to enrich uranium up to 4.5 percent – above the 3.67 percent allowed by the nuclear deal, though still far below weapons-grade levels of 90 percent.

Uranium enriched to 4.5 percent can be used at Iran’s Bushehr nuclear power plant, where a second reactor is under construction.

The concern is that the more uranium Iran enriches, the shorter will be the “breakout time” – the time it would need to produce enough material for a bomb. Analysts had put that time at a year if Iran abided by the 2015 deal’s restrictions.

At talks in Brussels on Monday, EU foreign ministers affirmed their support for the pact. The top diplomats from Britain, France and Germany later met for further discussions in Paris.

The three said they were “extremely concerned” that Iran had restarted enrichment at Fordo, and they called on Tehran to reverse course and comply with the agreement, formally known as the Joint Comprehensive Plan of Action, or JCPOA.

A meeting of all the signatories is likely to be held in coming days.

Iran has been open about its violations of the deal in recent months, announcing the moves before making them and allowing the IAEA to verify them.

Speaking at a U.N. General Assembly meeting in New York, Iran’s deputy U.N. ambassador, Eshagh Al Habib, insisted that his country’s moves are all “reversable.”

They provide “opportunity for remaining JCPOA participants either to take serious practical steps to preserve the JCPOA or, along with the U.S., accept the full responsibility for any possible consequences,” he said.

The head of Iran’s nuclear program, Ali Akbar Salehi, told the Associated Press on Monday that his country is producing much more low-enriched uranium.

Salehi said Iran is now turning out at least 5.5 kilograms (12 pounds) per day, compared with about 450 grams (1 pound) previously, thanks to the Fordo centrifuges.

One option for the other foreign powers is to trigger the dispute mechanism in the nuclear agreement, which would start the clock on a 30-day period in which to resolve the problem.

If the problem persists, the matter could be brought before the U.N. Security Council and could result in the “snapback” of sanctions that had been lifted under the deal.

“We affirm our readiness to consider all mechanisms in the JCPOA, including the dispute resolution mechanism, to resolve the issues,” the EU members of the agreement said after their Paris meeting.

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