International Atomic Energy Agency Director General Rafael Grossi says he is seriously concerned about Iran's increased stockpile of highly enriched uranium.



Grossi said at an IAEA Board of Governors meeting in Vienna, Austria, on Monday that Iran's stockpile of uranium enriched up to 60 percent increased to about 1.5-fold at 274.8 kilograms in the three months through February 8. That percentage is far above the limit set in an agreement Iran signed with world powers in 2015.



Iran says its nuclear development program is for peaceful purposes. But experts say uranium enriched to 90 percent or higher can be used to make nuclear weapons.



Iran has been under mounting pressure from Western countries. Iran said it activated a series of advanced centrifuges after the IAEA late last year passed a resolution criticizing Tehran for its poor cooperation.



Grossi said, "Iran is the only non-nuclear weapon State enriching to this level, causing me serious concern."



A landmark deal in 2015 with world powers restricted Iran's nuclear program in exchange for sanctions relief. But the administration of US President Donald Trump, during his first term in office, withdrew the US from the pact. In response, Iran is accelerating its nuclear development.



There are no signs that negotiations will resume anytime soon to revive a nuclear agreement, amid lingering tensions between the Trump administration in his second term and Iran.