The head of the International Atomic Energy Agency says Iran broke an IAEA law by failing to disclose much earlier its construction of a uranium enrichment facility.
In an interview with CNN-India, Mohamed ElBaradei said Iran was supposed to notify the IAEA on the day it began building the site.
He described Iran's failure to do so as a "setback to the principle of transparency," and said IAEA inspectors must visit the site as soon as possible to determine its purpose.
The head of Iran's nuclear agency, Ali Akbar Salehi, said this week Iran will soon tell the IAEA when it can inspect the site.
ElBaradei's comments came a day before officials from Iran and six world powers are to gather in Geneva for critical talks on Iran's nuclear program.
Iran acknowledged last week it is developing a new uranium enrichment facility, apparently after learning Western nations had long known of it. The site is near the holy Shi'ite city of Qom, about 160 miles southwest of Tehran.
The United States and other Western powers have insisted the IAEA gain immediate access to the facility to ensure it is not being built to produce atomic weapons.
The U.S. and its Western allies accuse Iran of seeking to develop nuclear weapons. Iran says its atomic program is for peaceful purposes to produce electricity.