The UN says Iran is curbing its atomic activities in line with a preliminary deal made in January.
A restricted report says Tehran has not resumed its previous enrichment of uranium to just a technical step from the level needed for a nuclear weapon, and continues to reduce its supply of that material.
The UN nuclear agency report, released late Thursday, also says major construction remains at a standstill at the Arak reactor, southwest of Tehran. If completed, the facility could produce substantial amounts of plutonium, which can arm nuclear warheads.
Tehran says it is not interested in nuclear arms and only seeks power production.
Iran and six world powers are working on a comprehensive agreement envisaging long-term limits on Tehran's nuclear programs in exchange for an end to sanctions.
