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.

The IAEA also criticized Iran for denying inspectors access to three sites where nuclear activity has taken place in the past. “As a result of its ongoing evaluations, the Agency identified a number of questions related to possible undeclared nuclear material and nuclear-related activities at three locations in Iran that had not been declared by Iran,” the agency said in a separate report.

Since the US departure from the international pact, the Trump administration has pursued a “maximum pressure” policy against Iran. After the US killing of Iran's second most powerful official, Gen. Qasem Soleimani, in January, Iran announced it would no longer be bound by certain aspects of the nuclear deal and specifically pointed to uranium enrichment and the number of centrifuges.

“The Islamic Republic of Iran will end its final limitations in the nuclear deal, meaning the limitation in the number of centrifuges,” the government said in a statement issued after an emergency meeting to discuss Soleimani's killing. “Therefore Iran's nuclear program will have no limitations in production including enrichment capacity and percentage and number of enriched uranium and research and expansion.”

Foreign Minister Javad Zarif said at the time that the announcement did not mean Iran was leaving the Joint Comprehensive Plan of Action, as the deal is formally known. Zarif also said Iran would continue to cooperate with the IAEA, allowing it to review its nuclear research, and would be willing to comply fully with the agreement again if sanctions against Iran were removed.

CNN has reached out to the Iranian foreign ministry for its response to the report.