WASHINGTON (AP) — U.S. authorities believe that Iranian-based hackers were responsible for cyberattacks that devastated Persian Gulf oil and gas companies, a former U.S. government official said. Just hours later, Defense Secretary Leon Panetta said the cyberthreat from Iran has grown, and he declared that the Pentagon is prepared to take action if American is threatened by a computer-based assault.

The former official, who is familiar with the investigation, said U.S. authorities believe the cyberattacks were likely supported by the Tehran government and came in retaliation for the latest round of American sanctions against Iran.

Before Panetta's remarks on Thursday, U.S. officials had said nothing publicly about the Gulf attacks or the investigation. But Panetta described them in a speech to business leaders in New York City, saying they were probably the most destructive cyber assault the private sector has seen to date.