Cox spoke after telling a conference hosted by the Atlantic Council think tank that the overall sophistication and danger of cyber threats is increasing at “an accelerating rate, not a linear rate.”

“So the potential for these things to do destructive damage is very high,” he said.

The United States is among the few countries reliably reported to have mounted a destructive keyboard-launched attack - against Iran’s disputed nuclear centrifuges using malicious code known as Stuxnet that surfaced in 2010.

Army General Keith Alexander, who simultaneously heads Cyber Command and the National Security Agency, told a forum in July that unspecified foreign countries, hackers and criminal gangs contributed to a 17-fold jump in cyber attacks on U.S. infrastructure from 2009 to 2011.

Promoting Cyber Command in the military hierarchy would simplify its operations in cyberspace and boost its ability to work directly with U.S. government agencies, allies and coalition partners.