Obama warns Russia of retaliation over hacking in US elections

The outgoing US president said he was waiting for a final report he has ordered into a range of Russian hacking attacks that may have swayed last month's tight election in which Republican candidate Donald Trump defeated Democrat Hillary Clinton.

"I think there is no doubt that when any foreign government tries to impact the integrity of our elections. That we need to take action and we will," Obama told the National Public Radio in a interview.

"At a time and a place of our own choosing. Some of it may be uh, explicit and publicised; some of it may not be," he said according to an excerpts of the interview released by NPR.

The full interview would be aired on Friday, before leaving for his annual family vacation in Hawaii.

"Um, but Mr Putin is well aware of my feelings about this, because I spoke to him directly about it," Obama said.

Obama has ordered US intelligence agencies to conduct a full review of the hacking and report back to him before he leaves office on Inauguration Day January 20.

Press Secretary Josh Earnest told reporters during the daily White House briefing that "Mr Trump obviously knew that Russia was engaged in malicious cyber activity that was helping him, (and) hurting (Democrat Hillary) Clinton ... "These are all facts that are not in dispute."

Earnest pointed out that Trump had encouraged Moscow during a news conference to find missing emails from Clinton's private server. Trump has said he was joking.

"I don't think anybody at the White House thinks it's funny that an adversary of the United States engaged in malicious cyber activity to destabilise our democracy," Earnest said. "That's not a joke."

Earnest, without mentioning Russian President Vladimir Putin by name, also said "only Russia's senior-most officials could have authorised these activities," repeating the words from an October US intelligence assessment.