New concerns are being raised that the nation's electrical grid and critical infrastructure are increasingly vulnerable to a catastrophic foreign attack -- amid speculation over whether officials are eyeing a former Cold War bunker, inside a Colorado mountain, as a "shield" against such a strike. 

North American Aerospace Defense Command is looking for ways to protect itself in the event of a massive electromagnetic pulse, or EMP, attack -- a deliberate burst of energy that could disrupt the electrical grid and cripple NORAD's ability to defend the nation. 

"What it could do, these various threats, is black out the U.S. electric grid for a protracted period of months or years," warned Peter Pry, executive director of the EMP Task Force, a bipartisan congressional commission. "Nine out of ten Americans could die from starvation, disease and societal collapse, if the blackout lasted a year." 

Pry said a $700 million contract to upgrade electronics inside Colorado's Cheyenne Mountain facility may provide a clue about just how worried the military is about the threat. 

The Air Force moved out of Cheyenne Mountain, which was built to survive a nuclear attack, in 2006, establishing its NORAD headquarters at Peterson Air Force Base in Colorado. But that facility, inside the mountain, could offer protection against a so-called EMP attack. 

The head of NORAD recently suggested, at an April 7 Pentagon press conference, that Cheyenne may still be needed. 

"My primary concern was, are we going to have the space inside the mountain for everybody who wants to move in there?" Adm. William Gortney told reporters. "I'm not at liberty to discuss who's moving in there, but we do have that capability to be there." 

NORAD spokesman Capt. Jeff Davis pushed back on the idea that NORAD is relocating its headquarters, but acknowledged its advantages in the case of an EMP attack. And he did say Cheyenne has served as an alternate command center since 2006.   

"We are not moving back to the mountain," Davis told Fox News. "The mountain's ability to provide shield against EMP is certainly a valuable feature, and that is one reason we maintain the ability to return there quickly if needed -- but we aren't 'moving back' per se." 

An electromagnetic pulse from a nuclear weapon being detonated in space would in essence fry the nation's electrical grid. 

Pry warned that the U.S. is vulnerable to a missile fired into space from a southerly route. Another threat: a naturally occurring geomagnetic storm like the solar superstorm that narrowly missed the Earth in 2012, according to NASA. 

"The grid is utterly unprotected from an EMP attack. It's not adequately protected from cyber or physical sabotage," Pry said in an interview with Fox News. "It's why North Korea and Iran want the bomb, have the bomb. North Korea has actually practiced this against the United States." 

Pry, whose congressional EMP commission issued its last unclassified report in 2008, says that the Obama administration has not followed basic recommendations from the bipartisan task force which outlined how the nation's electrical grid could be hardened and protected from this kind of attack -- for $2 billion. 

"Two billion dollars is what we give in foreign aid to Pakistan," Pry said. "If we suspended that for one year and put it toward hardening the electrical grid, we could protect the American people from this threat." 

The House of Representatives unanimously passed several pieces of legislation to protect the nation's power grid -- the GRID Act, the Shield Act and the Critical Infrastructure Protection Act -- but they died in the Senate. Some states are beginning to act on their own despite the protest of private power companies. 

The warning comes as other senior national security experts have said they are worried about a potential cyberattack targeting the nation's key infrastructure. 

Former National Security Agency chief Keith Alexander outlined the threat at the Aspen Institute's National Security Forum Preview, "Cyber Nightmare: Is the Worst Yet to Come?" 

"I am not confident that we have the wherewithal, with today's cyber capabilities and our sharing relationships, to actually defend the power and the other sectors like we should," Alexander said on April 29, when discussing a possible 'nuclear Pearl Harbor.' 

"Those are things that most concern me right now."

Jennifer Griffin currently serves as a national security correspondent for FOX News Channel . She joined FNC in October 1999 as a Jerusalem-based correspondent. You can follow her on Twitter at @JenGriffinFNC.