The United States is launching a program to detect cyberattacks on private US companies and government agencies running critical infrastructure such as the electricity grid and nuclear power plants, The Wall Street Journal reported on Wednesday.

The newspaper, citing "people familiar with the program," known as "Perfect Citizen," said the surveillance would be carried out by the National Security Agency (NSA), the super secret US electronic monitoring agency.

It would rely on sensors deployed in computer networks for critical infrastructure that would be triggered by unusual activity suggesting an impending cyberattack, the Journal said.

The newspaper said major US defense contractor Raytheon Corp. recently won a classified contract for the initial phase of the surveillance effort valued at up to 100 million dollars.

A US military official told the newspaper the program was "long overdue" and would not constitute a violation of privacy.

The Journal noted that US intelligence officials have grown increasingly concerned about suspected Chinese and Russian surveillance of computer systems that control the electric grid and other US infrastructure.

It said "Perfect Citizen" would concentrate on typically older computer control systems that have since been linked to the Internet, making them more efficient but also more vulnerable to cyberattack.

"Because the program is still in the early stages, much remains to be worked out, such as which computer control systems will be monitored and how the data will be collected," the Journal said.

It said the NSA would "likely start with the systems that have the most important security implications if attacked, such as electric, nuclear, and air-traffic-control systems."

NSA chief General Keith Alexander has been named to head the newly created US Cyber Command.

In a recent speech, he said the role of US Cyber Command is to "deter, detect and defend against emerging threats against our nation in cyberspace."

Alexander also said effective cybersecurity would involve partnering with the private sector and others.

"All of us in government recognize that we cannot do this without the help of industry, academia and our allies," he said. "Securing cyberspace is a team sport.

"Securing our networks is not just a (military) issue, it is a national security issue with implications for all instruments of national power," he said.