US Defence Secretary Robert Gates says the disclosure of Iran's secret uranium-enriching facility could force more economic penalties against a country reeling from serious social and political divisions. In an interview to CNN he played down the effectiveness of military strikes against the site, arguing that pressuring Tehran economically and diplomatically would have a better chance of changing the Tehran government's policies. Gates' comments come ahead of a meeting Thursday in Geneva involving diplomats from Iran, the US, Britain, France, Russia, China and Germany. Tehran's nuclear program is at the top of the agenda. Meanwhile, Iran's Atomic Energy Organisation chief Ali Akbar Salehi said Iran will keep its uranium enrichment level at up to five per cent much lower than bomb-grade.