Barack Obama: We will take action against Russia over election hacking
Video report by ITV News Washington Correspondent Robert Moore
Barack Obama vowed to retaliate against Russia over hacking during the presidential election.
The president said America will respond at a "time and place of our choosing", some of which might be publicised and some not.
He said he had spoken directly to Vladimir Putin about his feelings over the hacking.
When a foreign government tries to interfere in US elections, the nation must take action - "and we will", Mr Obama told US radio station NPR.
He added: "Some of it may be explicit and publicised, some of it may not be. But Mr Putin is well aware of my feelings about this, because I spoke to him directly about it."
The Obama administration suggested President Putin personally authorised the hacking of Democratic officials' email accounts in the run-up to the election and said it was "fact" that such actions helped Donald Trump's campaign.
The White House also attacked president-elect Trump himself, saying he must have known of Russia's interference.
No proof was offered for any of the accusations.
The claims of Russian meddling in the election have also heightened already debilitating tensions between Washington and Moscow over Syria, Ukraine and a host of other disagreements.
White House spokesman Josh Earnest said: "Only Russia's senior-most officials could have authorised these activities."
But US officials have not said that Mr Trump would have lost to Hillary Clinton on November 8 if not for Russia's assistance, nor has there been any indication of tampering with the vote-counting.
Meanwhile, Hillary Clinton attended a donor party last night and said she was proud as secretary of state to have stood up to Putin in support of democratic values after the 2011 Russian elections.
NBC sources added that she also told supporters not to lose heart and that they too will have to stand up for democracy in this country and abroad.
She did not mention Donald Trump at all, the sources added.