President Barack Obama said Friday he had confronted Vladimir Putin in person over allegations of Russian hacking when they met ahead of the US election, telling him to "cut it out" and promising a firm response.
Just five weeks before he leaves the White House, the outgoing president has vowed to retaliate against Moscow over the cyber-meddling, which US intelligence says was designed to help Republican Donald Trump defeat Hillary Clinton, a Putin critic.
"Our goal continues to be to send a clear message to Russia or others not to do this to us because we can do stuff to you," the US president told a year-end press conference, at which he went the furthest yet towards pinning direct blame for the hacks on Putin.
"Not much happens in Russia without Vladimir Putin," Obama said. "I mean, this is a pretty hierarchical operation last I checked, there's not a lot of debate and democratic deliberation, particularly when it comes to policies directed at the United States."
After being alerted over the summer to Russian cyber attacks on his and Clinton's Democratic Party, Obama said, his chief concern was to ensure the hacking did not escalate and hamper the vote counting last month.
"In early September when I saw President Putin in China, I felt that the most effective way to ensure that that didn't happen was to talk to him directly and tell him to cut it out and there were going to be serious consequences if he didn't," Obama said.
"And in fact we did not see further tampering of the election process," he added. Regarding specific acts of retaliation, Obama said some would be carried out publicly, but that in other cases, "the message will be directly received by the Russians and not publicized."
"At a point in time where we've taken certain actions that we can divulge publicly, we will do so," Obama said. "Part of why the Russians have been effective on this is because they don't go around announcing what they're doing," he added.
Obama also said there was "some evidence" of China curbing cyber espionage in response to US warnings. "I had to have the same conversation with President Xi (Jinping) and what we've seen is some evidence that they have reduced but not completely eliminated these activities," he said.
Obama's traditional year-end press conference -- held as tensions soar with Russia -- was expected to be closely watched by his elected successor Trump, who has pledged to foster closer ties with the Kremlin and has dismissed intelligence reports of Russian hacking.
The president warned that while Russia remained a minor world power in his view, it had shown the potential to undermine American values. "They are a smaller country, they are a weaker country," he said.
"But they can impact us if we lose track of who we are. They can impact us if we abandon our values. "Mr. Putin can weaken us just like he's trying to weaken Europe if we start buying into notions that it's okay to intimidate the press. Or lock up dissidents."
Obama voiced concern over polling that suggests a third of Republican voters approve of Putin, saying: "Ronald Reagan would roll over in his grave."
But he also reached out directly to Trump, saying: "My hope is that the president-elect is going to similarly be concerned with making sure that we don't have potential foreign influence in our election process." He urged Trump to back mounting calls for a "bipartisan, independent" look into the allegations of Russian meddling.
Such a process, he said, could "give the American people an assurance not only that votes are counted properly, that the elections are fair and free but that we have learned lessons about how internet propaganda from foreign countries can be released into the political bloodstream."