VIENNA (AP) — Iran has slowed its enrichment of uranium at nearly weapons-grade levels, a report by the United Nations’ nuclear watchdog seen by The Associated Press said Monday.

The confidential report comes as Iran and the United States are negotiating a prisoner swap and the release of billions of dollars in Iranian assets frozen in South Korea. Slowing its enrichment of uranium could serve as another sign that Tehran seeks to lower tensions between it and America after years of tensions since the collapse of its 2015 nuclear deal with world powers.

The report by the International Atomic Energy Agency said Iran has 121.6 kilograms (268 pounds) of uranium enriched up to 60%, a far-slower growth than in previous counts. An IAEA report in May put the stockpile of 60% uranium at just over 114 kilograms (250 pounds). It had 87.5 kilograms (192 pounds) in February.

Uranium enriched at 60% purity is just a short, technical step away from weapons-grade levels of 90%. Iran has maintained its program is peaceful, but the IAEA’s director-general has warned Tehran has enough enriched uranium for “several” nuclear bombs if it chose to build them.

Iran likely would still need months to build a weapon. U.S. intelligence agencies said in March that Tehran “is not currently undertaking the key nuclear weapons-development activities that would be necessary to produce a testable nuclear device.” The IAEA, the West and other countries say Iran had a secret military nuclear program it abandoned in 2003.

Iran’s 2015 nuclear deal limited Tehran’s uranium stockpile to 300 kilograms (661 pounds) and enrichment to 3.67% — enough to fuel a nuclear power plant. The U.S. unilateral withdrawal from the accord in 2018 set in motion a series of attacks and escalations by Tehran over its program.

While Iran has slowed the enrichment, the IAEA reported other problems with trying to monitor its program. An IAEA report seen by the AP said Iran had denied visas for agency officials, while the “de-designation of experienced agency inspectors” also challenged its work.

The IAEA also hasn’t been able to access surveillance camera footage since February 2021 under Iranian restrictions, while the only recorded data since June 2022 has been from cameras at a workshop in the Iranian city of Isfahan.

Iran has not acknowledged the visa denials previously. Iran’s mission to the United Nations in New York did not immediately respond to a request for comment over the reported visa denials.

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Associated Press writer Jon Gambrell in Dubai, United Arab Emirates, contributed to this report.