"We have not opted to engage in some of the same behaviors we are seeing," said Admiral Michael Rogers, who heads both the NSA -- the leading US electronic eavesdropping agency -- and the new US Cyber Command, the military body charged with online combat.

Asked in a Senate Intelligence Committee hearing if he had received orders from Trump to fight back against Moscow's meddling, Rogers said: "No, I have not."

Rogers denied claims that the agency is doing nothing to push back against Russian hacking, theft of US cyber secrets and other activities.

However, he acknowledged: "They have not paid a price that is sufficient to change their behavior."

Rogers echoed the comments he and five other US intelligence chiefs made two weeks ago at the House Intelligence Committee, where all said they had not been ordered by Trump to counter the Russians.

The US has accused Russia of actively interfering in the 2016 presidential election, stealing Democratic party communications and pushing out disinformation through social media.

It also accuses Moscow of stealing hacking secrets of the US intelligence community.

Rogers said an order for Trump is needed before the US intelligence community and military can undertake offensive online operations against the Russians.

"What I see on the Cyber Command side leads me to believe that if we don't change the dynamic here, that this is going to continue, and 2016 won't be viewed as isolated," he said.

But he said that at a lower level, the NSA and Cyber Command could take some unspecified actions to rebuff attackers.

Asked about the exchange in Congress, White House spokeswoman Sarah Sanders suggested the president does not need to act.

"Nobody is denying him the authority," she said of Rogers.