(CNN) Iran has nearly tripled its stockpile of low enriched uranium since November, indicating a significant jump in production, according to a confidential report issued by the International Atomic Energy Agency, the United Nation's nuclear watchdog.

In the March 3 report to member states, and obtained by CNN, the IAEA said that Tehran's stockpiles of low enriched uranium now far exceed 300 kilograms, the limit set by the 2015 Iran nuclear deal.

The report said that as of February 19, "the Agency verified that ... Iran's total enriched uranium stockpile... was 1020.9 kilograms (+648.6 kilograms since the previous quarterly report)."

Low enriched uranium is usually used in nuclear plants, while highly enriched uranium is used for nuclear bombs, but in theory, the increased stockpiles reduce the "breakout" time Iran would need to acquire enough weapons-grade material to create a bomb.

The IAEA report said Iran has dramatically increased the number of centrifuges it uses to produce the nuclear fuel, bringing about 1,000 of the machines back into use in recent months, including at the Fordow underground enrichment facility. Iran had agreed to halt enrichment activity at Fordow under the 2015 nuclear deal, which President Donald Trump left in 2018.

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