"We've made very clear that Iran will not develop a nuclear weapon. We will not tolerate an Iran that has a nuclear weapon," Panetta said.
"We've made clear that we will not tolerate an Iran that tries to block the Straits of Hormuz. A fifth of the oil of the world goes through those straits. They're international waters. We're not going to allow them to block that," he warned, terming these as red lines.
"If they cross one of those lines, then we have all options on the table - we, the United States, have all options on the table. But, as the Prime Minister of Israel himself said, that ought to be the last option, not the first," the defence secretary said.
The United States, he said, doesn't want an Iran that basically spreads violence around the world, which supports terrorism, that conducts acts of violence.
"They planned an attack here against ambassadors of other countries here in the United States," he said.
"So we're not going to tolerate that, and we've made that clear. And as a result, the international community has come together. We have implemented strong diplomatic sanctions, we have implemented very strong economic sanctions, and we're continuing to do that - sanctions that are in many ways crippling Iran, crippling their economy, isolating them from the rest of the world, and having an impact on Iran," he said.
Panetta said that the basic message to Iran is that it has to change its behaviour.