"Our economy, the nation's critical infrastructure, and many of our military operations depend on unfettered access to cyberspace," said Lieutenant General Keith Alexander, the director of the super-secret National Security Agency (NSA).

"As cyberspace continues to evolve and grow in complexity and importance, our nation must vigilantly maintain technological dominance and freedom to maneuver within this global domain," Alexander said.

"This advancement in technology comes with vulnerabilities for our nation that have not been adequately addressed," he said in prepared remarks to a subcommittee of the House Armed Services Committee.

"Maintaining freedom of action in cyberspace in the 21st century is as inherent to US interests as freedom of the seas was in the 19th century, and access to air and space in the 20th century," Alexander said.

The NSA chief said the Pentagon had increased its emphasis on cyberspace to reflect this modern reality.

"The rapid expansion and global dependence upon cyberspace required the defense department to evolve its warfighting doctrine to include cyberspace as a viable domain on par with the domains of land, sea, air and space," he said.

"Cyberspace is a perfect environment for United States adversaries to thrive and a domain that the United States must vigilantly protect," he said, while doing so in a manner "that protects our Constitutional liberties."

Besides heading the NSA, Alexander is also commander of the Joint Functional Component Command for Network Warfare, which is responsible for planning, coordinating and conducting offensive and defensive cyberspace operations.

Alexander welcomed a recent reorganization which placed the operation and defense of Pentagon networks under his operational control but said more was needed.

"The next steps in this transformation will require a more substantial reorganization," he said.

Alexander noted that the Department of Defense (DOD) was considering the establishment of a new unified command for cyber operations, under the US Strategic Command, that would be headquartered at Fort Meade in Maryland.

"The creation of a single sub-unified cyber command would provide the DOD with a command comprised of forces and capabilities better aligned to conduct cyber operations," he said.

Alexander also said better training was needed for members of the US military and private contractors involved in cyber security.

"The cyber security training provided to our service men and women, and the civilian and contractor workforce, is inadequate and must be improved," he said.

The results of a 60-day review of cyber security by the White House are due to be released soon amid speculation President Barack Obama will name a cyber "czar" to oversee information technology security for the US government.

No single agency is currently charged with ensuring government IT security and lawmakers have called for creating a powerful national cyber security advisor reporting directly to the president.

Plans to reorganize the US government's approach to IT security come amid a growing threat of cyber spying and attacks, including reported breaches of the US electricity grid and the F-35 fighter jet program.

All rights reserved. copyright 2018 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.