He said Hussein Kamel had ordered him to find a nuclear bomb trigger while other scientists pursued at least five different methods of separating uranium to make bomb-grade fuel.

"It did not include centrifuges," he said, referring to the machines used to enrich uranium gas and produce bomb-grade nuclear fuel.

Someday a few weapons' worth of bomb-grade fuel from research reactors could end up in the hands of terrorists or dictators.

The governments that have signed the treaty regard the technique as a certain means for detecting clandestine diversions of bomb-grade fuel.

(Reprocessing involves chemically separating plutonium from other nuclear waste products, a procedure that can lead to production of bomb-grade fuel.)

To the Editor: Your June 12 front-page article on stalled efforts to buy bomb-grade fuel from Russia overlooks important flaws in the agreement.

In September, the agency revealed that as early as 1995, Pakistan was providing Tehran with the designs for advanced centrifuges capable of making bomb-grade nuclear fuel.

Agency teams came around twice a year to look at bomb-grade fuel that could be converted to weapons in two to three weeks.

The administration never expected India's nuclear establishment to give up its ability to make bomb-grade fuel.

Anti-proliferation organizations have long argued that reprocessing creates bomb-grade nuclear fuels that could be converted into weapons.