The International Atomic Energy Agency (IAEA) said Monday that Iran has enriched uranium past the 3.67 percent limit agreed in the 2015 nuclear accord, confirming an earlier announcement by the Iranian regime.

The confirmation by the UN nuclear watchdog came amid warnings from Tehran that the county could soon start enriching uranium up to 20 percent — just a step away from weapons-grade levels.

A spokesperson for the IAEA, the body tasked with verifying Iranian compliance with the Joint Comprehensive Plan of Action (JCPOA), said its Director General, Yukiya Amano, had informed the Board of Governors that its inspectors verified Monday “that Iran is enriching uranium above 3.67 percent.”

Iran has already breached one key element of the accord since the United Stated announced last year that it was withdrawing from the flawed agreement, which failed to require adequate inspection of Iran’s nuclear facilities and gave the Iranian regime billions of dollars in sanctions relief. Last week, the country announced that it had breached the 300 kilograms of low-enriched uranium allowed under the JCPOA.

“Let me be clear: Iran should not confuse American restraint with a lack of American resolve,” U.S. Vice President Mike Pence said, reiterating Washington’s stance on the dispute. “We hope for the best, but the United States of America and our military are prepared to protect our interests and protect our personnel and our citizens in the region,” he added.

A spokesperson for the European Union said that the bloc was alarmed by Tehran’s announcement that the Islamic Republic was producing material with a fissile purity of 4.5%.

“We are extremely concerned at Iran’s announcement that it has started uranium enrichment above the limit of 3.67%,” Maja Kocijancic said. “We strongly urge Iran to stop and reverse all activities inconsistent with its commitments (…) We are in contact with the other JCPOA participants regarding the next steps under the terms of the JCPOA, including a joint commission,” she added.