Steps must be taken to make sure the national grid can be stabilized in the event of a natural disaster or physical attack against grid infrastructure, a U.S. government official said.

Speaking at an Environmental and Energy Study Institute forum in Washington, Jon Wellinghoff, chairman of the Federal Energy Regulatory Commission, said the possibility of attacks on key transmission stations is one of the biggest risks the grid faces, Platts news service reports.

Wellinghoff said each of the three U.S. interconnections -- Eastern, Western and Texas -- is particularly vulnerable because their operations hinge on a number of high-voltage transmission substations.

"So we need to do what we can to minimize those vulnerabilities by ensuring that we can isolate portions of each one of those interconnects," he said.

Wellinghoff said "physical security issues ... certainly have to be dealt with. I think the biggest risk is potentially attacks on the system at those critical nodes."

Sen. Edward J. Markey, D-Mass., in a statement Wednesday commemorating the 12th anniversary of the Sept. 11, 2001, terrorist attacks on New York and Washington, warned "one of the single greatest threats to our national security is the vulnerability of our country's electric grid to attack."

Markey is a former senior member of the House Homeland Security Committee.

"National security experts agree that America's grid remains vulnerable to cyberattack that could result in widespread blackouts and devastate our security, economy and health," Markey said.

He called for legislation that would give the federal government authority to protect against cybersecurity threats and hold the utility sector "to the toughest possible security standards."

The New York Times reported this week more than 200 of the nation's utilities and government agencies are expected to participate in a cyberattack drill this fall.

Organized by the North American Electric Reliability Corp., the exercise is intended to address how the country would respond to a massive grid failure that interrupts supplies of water, food and fuel.

Utility industry leaders, at a conference organized by the Bipartisan Policy Center in Washington last month, said the sector needs to mobilize manpower, money and other resources to counter the growing threat of cyberattacks, as is done for natural disasters.

"We have to treat the cyberthreat with the same respect that we give to forces of nature that impact our grid -- hurricanes, floods, ice," Chris Peters, vice president for critical infrastructure protection at Entergy was quoted by the Houston Chronicle as saying at the conference.

Peters said the company already has a five-year plan to bolster resources to counter cyberattacks.