Iran will step up its uranium enrichment program by sharply increasing the number of centrifuges used to make nuclear fuel, a senior official said Wednesday, in direct defiance of Western demands. The statement by Iran’s nuclear chief, Fereidoun Abbasi, is likely to escalate tensions. The West suspects Iran’s nuclear program could be headed toward weapons production and has imposed punishing sanctions to try to persuade Tehran to stop enrichment. Iran has denied the charges, saying its program is peaceful and geared toward generating electricity and producing radioisotopes to treat cancer patients. …