Las Vegas (CNN Business) Crushing sanctions from the United States have sent Iran's economy into a "tailspin," ex-CIA director David Petraeus told CNN Business.

Petraeus, who was also America's top general in the Middle East, warned that Iran's economy could continue to nosedive "as we tighten the screws a few more turns."

Despite soaring tensions between Washington and Tehran, the former CIA director isn't overly concerned about an all-out war breaking out.

"Certainly, if Iran were to precipitate that, it would be a suicide gesture," Petraeus said from the sidelines of the SALT Conference in Las Vegas. "It would be very, very foolhardy. And they know that."

The bigger risk, the former head of US Central Command said, is "inadvertently ending up in some kind of clash" with militias trained and funded by Iran.

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