Defense Secretary Leon Panetta issued a call to arms against cyber attacks on U.S. targets and said the Pentagon must be prepared to launch preemptive attacks in cyberspace against potential attackers. He warned that a cyber attack by a nation state or terrorists on the U.S. could be America's "cyber Pearl Harbor" and "be just as destructive as the terrorist attack of 9/11."

In a speech before business executives in New York, Panetta revealed that cyber intruders have already gained access to some of America's critical control systems that run chemical, electric and water systems with the intent to "cause panic, destruction and loss of life."

With a current annual budget of $3 billion for cybersecurity, Panetta urged that more needs to be done to create an army of "skilled cyber warriors" to confront the immediate and growing threat. The Defense Department is already hammering out new "rules of engagement" for a potential cyber war.

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Panetta stressed that defending against potentially disastrous cyber attack on America will take a total government and business-wide effort. 

Panetta said that before the 9/11 terrorist attacks, warning signs went largely ignored.

"We cannot let that happen again," Panetta warned. "This is a pre-9/11 moment. The attackers are plotting."

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Updated at 6:40 a.m. ET: An aircraft used by U.S. Joint Chiefs of Staff chairman Martin Dempsey was damaged by rocket-fire at an airbase outside Kabul, Afghanistan, NATO said on Tuesday. The general was not on board at the time and no one was injured.

At around 1 a.m. (4:30 p.m. ET) on Tuesday, insurgents fired rockets or mortars into the base airfield, a source in Bagram Air Field told NBC News.  Two landed  in the air field, with one of them hitting the plane used by Dempsey, the source added. 

Massoud Hossaini / AFP - Getty Images

Chairman of the US Joint Chiefs of Staff, General Martin Dempsey (C) poses at NATO's International Security Assistance Force (ISAF) headquarters in Kabul on Monday.

Meanwhile, NATO's mission in Afghanistan confirmed that the plane had been damaged by incoming fire, saying it had been hit by "shrapnel from an indirect fire round."

"The round was one of two that impacted Bagram last night. An ISAF helicopter was also damaged," the ISAF statement added.

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"(Dempsey) was nowhere near the aircraft. We think it was a lucky shot," NATO senior spokesman Col. Thomas Collins told Reuters.

A new plane was brought in for Dempsey and he and his crew departed later in the morning.

The aircraft was only being used temporarily by Dempsey and his staff. 

Bagram targeted
Dempsey had been in the country on a two-day visit for talks with NATO and Afghan commanders on a string of recent rogue shootings. 

Bagram is occasionally targeted with rockets and mortar shells fired by insurgents from surrounding hills and fields. 

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Sporadic attacks also occur at NATO's other main airbase in Afghanistan, Kandahar Airfield, in the volatile south, although they rarely cause deaths or major damage. 

Before leaving Afghanistan, Dempsey met his Afghan counterpart, General Sher Mohammad Karimi, who raised the issue of insider attacks by rogue forces that have killed 10 American troops in the past two weeks. 

"In the past, it's been us pushing on them to make sure they do more," he said on Monday. "This time, without prompting, when I met General Karimi, he started with a conversation about insider attacks -- and, importantly, insider attacks not just against us, but insider attacks against the Afghans, too." 

Reuters and The Associated Press contributed to this report.

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