WASHINGTON (AP) -- Russia and China present the greatest cyber security threat to the U.S., but Iran is trying to increase and spend more on its capabilities, the Navy admiral in charge of the military's Cyber Command told Congress Tuesday.

Adm. Michael Rogers told the Senate Armed Services Committee that while the U.S. has more overall military power than the three countries, the gaps are narrower when it comes to cyber warfare.

He said U.S. Cyber Command is making progress building cyber mission teams, and will have 133 fully operational by September 2018. Already, he said that nearly 100 teams are already conducting cyberspace operations.

Defense Secretary Ash Carter has beefed up the use of offensive cyber warfare in Iraq and Syria and made increasing the department's cyber capabilities a key goal.

As part of that, he is considering elevating Cyber Command to a full, independent military command. Currently U.S. Cyber Command is a sub-unit of the military's Strategic Command.

During testimony on Tuesday, Rogers told senators that being designated a full command would allow his units to "be faster, which would generate better mission outcomes."

He added that it also would give him more input into the budget process and how to prioritize spending.

A senior U.S. official said Tuesday that Carter believes that making Cyber Command a full command would be worthwhile. The official said that while discussions with the White House are ongoing, Carter has not yet sent his final recommendation to the president. Congress would also need to approve such a change.

The official was not authorized to discuss the matter publicly so spoke on condition of anonymity.

During the hearing, Rogers said that his major cybersecurity concerns include attacks against critical infrastructure in the U.S. and the possibility that cyber hackers may begin breaching networks and changing data, rather than just reading it or stealing it. As a result, he said, officials would no longer be able to "believe what we're seeing," including in data that the military need for critical operations.

In addition, he said that there are increasing worries that extremist groups and others may begin to view cyber as a weapons system and "want to use it as a vehicle to inflict pain against the United States and others."

By AP