Fox isn't the first to make the 2012 claim. The director of the CIA did so last year. And a recent article by the former UN weapons inspector David Albright and Andrea Stricker – which I arrived at via Jeffrey Goldberg – explains just how Iran might pull it off, in spite of recent setbacks:
"Technically, Iran could decide to build a nuclear weapon now using the Natanz enrichment plant. The United States has estimated that Iran could produce enough weapon-grade uranium for a bomb in about one year. ISIS estimates Iran could halve that time to six months with advance preparation, and with somewhat better operation of the IR-1 centrifuges. U.N. experts say Iran knows enough now to build a crude weapon but faces problems in missile delivery.At the same time, there is wide international consensus behind the U.S. estimate that Iran is unlikely to use the Natanz plant to dash to weapons in 2011 or 2012. It would have to divert a stock of low-enriched uranium under safeguards. Iran could try to delay inspectors' access to the enrichment plant, but the inspectors are highly likely to detect this diversion within two months, long before Iran could produce enough weapon-grade uranium for a bomb. The resulting international condemnation, and possible military strikes, would likely deter Iran from even trying to use Natanz.In the longer term, thwarting Iran's growing options to develop a nuclear weapon remains a major challenge. If Iran built a secret site using more advanced centrifuges, it could be ready to build a bomb as soon as 2012 or 2013."