Iran has told U.N. nuclear officials that it plans to add potentially hundreds of next-generation centrifuge machines to its main uranium enrichment plant, a move that could dramatically boost its ability to produce the fuel used in nuclear power plants and — potentially — nuclear bombs.

The notification was delivered in a letter last week in which Iran said it would begin installing the more powerful centrifuges at its Natanz plant, south of Tehran, which already has been enriching uranium for nearly a decade, according to a Western diplomat briefed on the plans.

The new machine, the IR2M, is believed to be vastly superior to the clunky, 1970s-era IR1 machine that Iran currently uses, giving Iran the ability to produce up to four times as much enriched uranium per machine. Iran claims the enriched uranium would be used exclusively for nuclear power plants, but U.S. officials suspect that Iran is using nuclear energy to keep open its options to pursue a weapons program.