VIENNA, 6 March 2007 — Iran’s persistent failure to clear up concerns about its nuclear activities after concealing them for almost 20 years sets it apart from all other nations, the UN atomic watchdog chief said yesterday. Six world powers are now negotiating on widening sanctions against Iran for pressing ahead with its program to enrich uranium, a possible route to building atomic bombs, and ignoring a Feb. 21 UN Security Council deadline for it to stop.

“Iran’s verification case is sui generis (one of a kind),” Mohamed El-Baradei, director of the International Atomic Energy Agency, said in opening remarks to a gathering of the IAEA’s 35-nation board of governors.

“Unlike other verification cases, the IAEA’s confidence about the nature of Iran’s program has been shaken because of two decades of undeclared activities (until 2003),” he said.

“This confidence will only be restored when Iran takes the long overdue decision to explain and answer all the agency’s questions and concerns about its past nuclear activities in an open and transparent manner,” El-Baradei added.

Iran rejects Western suspicions that it is trying to master nuclear bomb technology under the cover of a civilian atomic energy program, saying it only wants to generate electricity.

Tehran has also complained of unfair treatment, noting the IAEA has found no hard evidence of covert bombmaking efforts. It has characterized sanctions as a US-led campaign to stunt its economic development and topple its government.