America's electrical grid is vulnerable to a terrorist attack, security experts say.

Experts warn if a nuclear weapon was detonated, electrical grids would be stopped and that could disrupt everything from communications networks to military defenses.

Such an event would involve what is called an EMP, or electromagnetic pulse. An EMP is a large wave of energy powerful enough to knock out systems that control the flow of electricity across the nation.

The Federal Energy Regulatory Commission says the U.S. is currently unprepared to stop or recover from an EMP.

"The consequences would be catastrophic," said Joseph McClelland, director of the Energy Commission's Office of Electric Reliability.
     
USA Today reports the commission is now pushing Congress for authority to take protective steps.

They want power companies to build metal shields around sensitive computer equipment. They say it could cost up to $2 trillion to repair a damaged grid.