An American official has criticized Iran's offer to be more open about its nuclear activities, calling it a “charm offensive” that does not resolve international concerns about possible threats from the program.

U.S. envoy Glyn Davies said Wednesday that Iran is “flouting” its obligations by continuing sensitive nuclear activities despite United Nations Security Council demands for a suspension. He was speaking at a meeting of the U.N. nuclear agency's governing board in Vienna.

Davies also said a recent Iranian letter to European Union foreign policy chief Catherine Ashton does not contain any new commitments to address international concerns about Iran's possible aim of producing nuclear warheads.

U.N. agency chief Yukiya Amano said Monday he is “increasingly concerned” about new intelligence from agency members suggesting Iran is engaged in such experiments.

Amano said Iran is showing “greater transparency” than usual about its nuclear program but is not providing “necessary cooperation” with the agency on nuclear matters.

European Union nations told Wednesday's IAEA meeting that Amano's report to the agency shows Iran is “advancing in an extremely concerning direction.”

Iran says its nuclear program is intended only to generate electricity for peaceful purposes.