The U.N. agency monitoring the nuclear pact between Iran and six world powers is reporting that Iran's stockpile of heavy water is marginally over the allowed limit but Tehran plans to return to compliance.

The deal specifies a heavy water limit of 130 metric tons (143.3 tons.) The confidential report seen by The Associated Press that was issued Wednesday says that Iran's stockpile exceeded that amount by 0.10 metric tons.

Heavy water is a potential proliferation concern because it is used in reactors that produce substantial amounts of plutonium, a potential path to nuclear weapons. Iran already overstepped the limit in February when some of the excess was exported to the U.S.

The report notes that Tehran has announced plans to export 5 metric tons to an unspecified country.