NEW : The Fordo says the enrichment is `` further escalation '' by Iran . The Kayhan confirms uranium enrichment has begun at the U.S. plant . Last month , U.S. President Barack Obama announced sanctions against Iran 's central bank . U.S. says its nuclear program has a medical purpose , a semi-official newspaper reports . Iran needs to enrich uranium to up to 20 % for radioisotopes to treat cancer , Kayhan reports .
NEW : The Fordo says the enrichment is `` further escalation '' by Iran . The Kayhan confirms uranium enrichment has begun at the U.S. plant . U.S. says its nuclear program has a medical purpose , a semi-official newspaper reports . Iran needs to enrich uranium to up to 20 % for radioisotopes to treat cancer , Kayhan reports .