Iran's nuclear ambitions are the greatest current threat to global security, according to US Defense Secretary Robert Gates. "Iran is the one that concerns me the most because there don't seem to be good options (or a scenario) where one can have any optimism that good options will be found," Gates told the Economic Club of Chicago. The threat rests not only in Iran's apparent determination to seek a nuclear weapon, but in the "inability of the international community to affect their determination to do that," Gates said. "All of the outcomes are negative," he said. "If they achieve one, the possibility of a nuclear arms race in the Middle East is very, very real.