TEHRAN, Iran – In a bid to ease international concerns over its nuclear program, Iran has converted more than a third of Tehran's most highly enriched uranium into a powder for a medical research reactor that is difficult to reprocess for weapons production, experts and U.N. monitors say.

The work – noted in a technical report by the U.N.'s nuclear watchdog agency in late August – suggests Iran is trying to display enough goodwill to restart nuclear talks with world powers, while aiming to soften demands by the U.S. and others to halt Tehran's top-level uranium enrichment.

An influential Iranian parliament member, Hossein Naqavi, said the country was taking a "serious and concrete confidence-building measure" by converting some of the 20 percent enriched stockpile into U3O8, or uranium oxide, in the form of powder.