The Pentagon plans to assign significantly more personnel to counter increasing cyber threats against the U.S. government.
The plan, which would increase both military and civilian staffing at U.S. Cyber Command, comes as the Pentagon moves toward elevating the new command and putting it on the same level as the major combatant commands.
The official said no formal decisions had been made on the expanding staffing levels or changing Cyber Command into a "unified" command like U.S. Strategic Command, which currently oversees cyber command and the U.S. nuclear weapons arsenal.
Any changes to the combatant command structure would be made based on strategic and operational needs, and take into account the need for efficient use of taxpayer dollars, said the official, who was not authorised to speak publicly.
The Pentagon was working closely with U.S. Cyber Command and the major military commands to develop "the optimum force structure for successfully operating in cyberspace," the official said.
The Washington Post, quoting senior defence officials, reported that the Pentagon had decided to expand Cyber Command's current staffing level of 900 to 4,900 in coming years.
The official confirmed that Cyber Command planned to expand its force significantly, but said the specific numbers cited by the Post were "pre-decisional."
The newspaper said senior Pentagon officials had agreed to increase the force late last year amid a string of attacks, including one that wiped out more than 30,000 computers at a Saudi Arabian state oil company.
The plan calls for creating three types of force under the Cyber Command, said the defence official.
"National mission forces," would protect computer systems that undergird electrical grids and other kinds of infrastructure.
"Combat mission forces," would help commanders abroad execute attacks or other offensive operations, while "cyber protection forces," would focus on protecting the Defence Department's own systems.
Details were still being worked out, the official said.