The U.S. military must reorganize its cyber operations and will use a new command at a Maryland Army facility to create a force for digital warfare, the director of the National Security Agency said Tuesday.

Lt. Gen. Keith Alexander, the Pentagon's leading cyber warfare commander, said the U.S. is determined to lead the global effort to use computer technology to deter or defeat enemies, while still protecting the public's constitutional rights.

In testimony prepared for delivery to a House Armed Services subcommittee, Alexander and other military leaders in cyber matters outlined the challenges to keeping up with rapidly changing technologies and the need for more resources and training. In blunt comments, Alexander acknowledged that cyber training for the Pentagon's work force is inadequate and must be improved.

In separate prepared testimony, Lt. Gen. William Shelton, the Air Force's chief of warfighting integration, said the Pentagon relies heavily on industry efforts to respond to cyber threats. That approach, he said, does not keep pace with the threat.

The testimony was set to come as the Obama administration prepares to release its review of the nation's cybersecurity, and on the heels of a critical report by the National Research Council. The independent group's report concluded that the government's policies on how and when to wage cyber warfare are ill-formed, lack adequate oversight and require a broad public debate.

Alexander said the military's new cyber command at Fort Meade, Md., will be a sub-unit of U.S. Strategic Command, and would be designed to "defend vital networks and project power in cyberspace."

Defense Department networks are probed repeatedly every day and the number of intrusion attempts have more than doubled recently, officials have said.

In a report released Tuesday, the Government Accountability Office said the number of cyber threats or incidents reported by federal agencies ballooned from about 5,500 in 2006 to more then 16,800 last year.

The incidents, which were reported to the U.S. Computer Emergency Readiness Team, mostly involved unauthorized access to the system, violations of computer use policies or investigations into unconfirmed incidents that were potentially harmful. But US-CERT noted that 14 percent of the incidents involved malicious computer codes, 12 percent were scans, probes or attempts to access the system, and 1 percent were successful attacks that impaired the network or system.

The GAO report repeated what has become a federal mantra: The cyber threats to U.S. computer systems are growing and becoming more sophisticated, and range from criminals trying to steal data to hackers looking for mischief and terrorists hoping to steal or destroy information or networks.

Military leaders said earlier this month that the Pentagon spent more than $100 million in the past six months responding to and repairing damage from cyber attacks and other computer network problems.