“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.

“If something is done to prevent them from getting one, the consequences of that are completely unpredictable and frankly, very bad.”

Gates said he has struggled to convince other nations, particularly Russia, that the Iranian situation threatens more countries than just the United States.

“Iran’s going to have the capability to deliver nuclear weapons to the people in their region a lot sooner than they’re going to have the capability to deliver them to us,” he said.