Vienna, Austria ? The chief U.N. atomic watchdog chided Iran on Monday for delays in divulging key information about its nuclear program, saying the onus is on Tehran to overcome a “confidence deficit” caused by past cover-ups.

As Mohammed ElBaradei criticized Iran at a meeting of the International Atomic Energy Agency, the Bush administration suggested it was considering a major strategy shift — joining Europe in offering Tehran economic incentives to abandon its uranium enrichment program.

Russia, meanwhile, sought to dismiss concerns that an Iranian reactor it built and will supply with fuel could be used to develop weapons. The accord is key to bringing Tehran’s first reactor on line.

The deal was struck despite American objections, although U.S. officials said they could live with the pact because it was designed to eliminate the possibility of the Iranians misusing the fuel.

More worrisome for the United States and European nations are Iran’s plans to enrich its own uranium.

While Iran says it wants the technology only to generate electricity, the process also can produce weapons-grade material for warheads, and Washington contends that is the main reason Tehran is interested in enrichment.

Iran has suspended work on enrichment pending negotiations with France, Germany and Britain but has repeatedly said the freeze is of short duration, despite European hopes that Tehran will commit to fully scrapping its program.

A two-year investigation by the U.N. nuclear agency established that Iran ran a clandestine nuclear program, including uranium enrichment, for nearly two decades.

Iran and North Korea are considered the greatest nuclear threats and the board’s meeting this week will focus on them. The agency has little leverage with North Korea, which quit the agency two years ago and claims to have atomic weapons, but diplomats said the board likely would urge the communist state to return to six-nation talks meant to defuse the threat.