VIENNA (AP) -- Diplomats say Iran is moving ahead to update a program the West fears could be used to make nuclear weapons, in a blow to years of high-level diplomacy aimed at stopping it from doing so.

Three diplomats say Tehran now has installed about 700 high-tech centrifuges in an upgrade of its uranium enrichment program since the start of the year. That represents an increase of about 100 since mid-April.

Tehran says it is enriching uranium only for peaceful uses. But the U.S. and its allies fear Tehran may enrich to levels used for nuclear bombs.

The International Atomic Energy Agency is expected to report on the development Wednesday. The diplomats, all from IAEA member nations, demanded anonymity because they are not authorized to divulge confidential IAEA information.