VOA Persian's Katherine Ahn contributed to this report.
WASHINGTON — The United Nations' atomic energy agency has confirmed Iran has surpassed the uranium enrichment limits spelled out in the 2015 nuclear deal.
The International Atomic Energy Agency said its inspectors verified Monday that Iran has surpassed the 3.67% enrichment limit set in the accord, aimed at restraining Tehran's ability to develop nuclear weapons in return for sanctions relief.
It did not specify by how much Iran exceeded the limit, but the Associated Press quotes a spokesman for Iran's Atomic Energy Organization on Monday as saying Tehran had enriched uranium to "around 4.5%" purity.
Iran earlier said it could enrich uranium to 20% as it backs away from its commitments under the nuclear deal.
Uranium enriched to 5% is sufficient to produce fuel for nuclear power plants, but still far below the 90% needed for building a nuclear weapon.
U.S. President Donald Trump withdrew the United States from the nuclear deal last year and imposed tough sanctions on Iran.
Tehran has already pulled out of parts of the agreement and is threatening to move further and further away from it unless the remaining parties — Britain, China, France, Germany and Russia — provide economic relief from the crippling U.S. sanctions.
WATCH: US warns Iran
The European Union said it was "extremely concerned" about Tehran's action.
"We strongly urge Iran to stop and reverse all activities that are inconsistent with the commitments" it had made under the international agreement, the EU said in Brussels.
French President Emmanuel Macron's chief diplomatic adviser is visiting Tehran this week to discuss the situation.
Russia said it is concerned about the Iranian action. But Kremlin spokesman Dmitry Peskov said it had warned that Trump's withdrawal from the pact would have negative consequences for global security.
Trump has warned Iran that it "better be careful."
National Security Adviser John Bolton added Monday that the U.S. "will continue to increase the pressure on the Iranian regime until it abandons its nuclear weapons program and ends its violent activities across the Middle East, including conducting and supporting terrorism around the world."
Tehran long has insisted that its nuclear program is only for peaceful purposes.
Columbia University researcher Richard Nephew, who was part of a U.S. team negotiating with Iran under Trump's predecessor Barack Obama, said Tehran's latest breaking of a nuclear deal commitment does not mean it is racing toward developing a nuclear weapon.
"What Iran is doing is going to shorten the timeline [for nuclear weapon development] by a measure of days, and in time, a measure of weeks," Nephew told VOA Persian in a Monday interview. "But Iran still is a year away from being able to produce a nuclear weapon and will [remain so] for some time to come."
But retired U.S. Marine Corps Lieutenant Colonel Dakota Wood, a senior defense researcher at the conservative Heritage Foundation in Washington, said Iran's latest moves demonstrate the viability of its perceived nuclear weapons program.
"Because [Iran] didn't have to dismantle any of its infrastructure under the  deal, it can quickly continue exceeding the [low-enriched uranium] quantity limit of 300 kilograms and then further enrich [to higher purity]," Wood said in a separate VOA Persian interview Monday. "So going to 4.5% purity, being on a track to 20% and then ultimately to 90% if they decide to go down that path, really reveals the organic, inherent capabilities [Iran] has in its nuclear program."
Both Wood and Nephew said they believe Iran is using its breaches of the nuclear deal as leverage to win diplomatic concessions from the West.