at Natanz was attacked. But another fear is that they intended to enrich uranium more highly at the secret plant, to a level suitable for a nuclear explosion. The discovery will strengthen the demands by the US and its allies for further sanctions to be imposed on Iran unless it suspends all enrichment, as required by the Security Council. Iran on defensive over secret site "Iran must comply with UN Security Council resolutions and make clear it is prepared to meet its responsibilities as a member of the community of nations," Mr Obama said. Tehran would be held accountable for any failure to meet these responsibilities, he said. Speaking after Mr Obama, the French and British leaders used strong language to insist that Iran would now have todisclose full details of its entire nuclear programme or face new and tougher sanctions. Gordon Brown stressed that the US, France and UK were "at one" on the issue, and accused the Iranians of "serial deception". There was now "no choice but to draw a line in the sand" over the nuclear issue, he said. "Iran must abandon any military ambitions for its nuclear programme." Mr Sarkozy said the situation was a challenge to the entire international community. "Everything must be put on the table," the French president said, adding that the world needed to see a "step change" from Iran in the coming months. Russian President Dmitry Medvedev, informed of the plant's existence by Mr Obama this week, said the second plant was against the requirements of