Congress’ failure to pass cyber security legislation this summer was very disappointing, Carter told Reuters after the speech, noting that the proposed measure would have helped increase U.S. cybersecurity “tremendously”.

As a result, he said, the Obama administration was trying to move ahead on its own, within existing legislative constraints.

“We’re trying to do without legislation some of the things -- obviously we can’t do everything -- that we need to do,” he said.

White House homeland security adviser John Brennan last month said the White House was exploring whether to issue an executive order to protect the nation’s critical computer infrastructure, but gave no details on the timing or possible content of such an order.

Senator Jay Rockefeller, who heads the Senate Commerce Committee, on Wednesday sent letters to the 500 biggest U.S. companies, challenging them to step up their computer security and blaming the defeat of the legislation on concerns raised by “a handful of business lobbying groups and trade associations.”

He asked the companies to identify their own best practices and to spell out their concerns about government-conducted risk assessments that were part of the cybersecurity bill. He warned that the companies could face “reactive and overly prescriptive legislation” if nothing was done until some cyber disaster.

Carter told hundreds of industry executives and military officials at the conference that protecting the country’s privately-controlled computer networks raised myriad antitrust and privacy questions that needed to be addressed more quickly.

Some of those questions center on the amount and type of data that can be shared among private companies and with the government, and to what extent the government can get involved in protecting private networks.

The Pentagon is facing mounting budget pressures, especially if Congress fails to avert an additional $500 billion in across-the-board defense cuts due to start taking effect in January.

Carter said the budget reductions would have a devastating effect on a number of Pentagon programs, but continued investment in offensive and defense cyber operations would continue, along with unmanned systems, space capabilities and electronic warfare.