President Barack Obama vowed to send a "clear message" to Russia for trying to sway the US election, while calling on Donald Trump and Republicans to put national security before politics.
Obama all-but accused Russian President Vladimir Putin of personally ordering an audacious cyber hack that many Democrats believe gravely wounded Hillary Clinton in a closely fought election.
The US intelligence community has concluded that a hack-and-release of the Democratic Party emails was designed to put Trump -- a political neophyte who has praised Putin -- into the Oval Office.
But with tensions rising between the world's two preeminent nuclear powers and US political anger near boiling point after Trump's shock election, Obama sought to exude calm while promising a measured response.
Assuring Americans that the ballot itself was not rigged, he promised to "send a clear message to Russia or others not to do this to us, because we can do stuff to you."
Noting that "not much happens in Russia without Vladimir Putin," Obama said he had personally told the former KGB officer when they met in September to "cut it out."
"In fact, we did not see further tampering of the election process," he told journalists before heading for his Christmas vacation in Hawaii.
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."
Obama's comments come as Putin registered a major propaganda victory in Syria and became a focal point of American political debate.
Despite those coups, Obama belittled Russia as a second rate power with little going for it, using language that is sure to infuriate the status-conscious Russian leader.
"The Russians can't change us or significantly weaken us. They are a smaller country, they are a weaker country, their economy doesn't produce anything that anybody wants to buy except oil and gas and arms. They don't innovate."
- Ronnie's grave -
But Obama's sternest message may have been for Trump and other Republicans who have played down the cyber attack.
"Over a third of Republican voters approve of Vladimir Putin," Obama said citing a recent poll. "Ronald Reagan would roll over in his grave. How did that happen?"
Obama urged the president elect -- who has repeatedly questioned Russia's involvement -- to accept an independent nonpartisan investigation.
"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."
While Obama has ordered his own inquiry, a political battle is already being waged in Washington between Republicans who want a Congressional process they can control and Democrats who want to see something like the bipartisan 9/11 Commission.
"One way I do believe the president-elect can approach this that would be unifying is to say that we welcome a bipartisan, independent process," Obama said.
The outgoing president rejected suggestions that he had been slow to respond to the claims of Russian interference.
"My primary concern was making sure that the integrity of the election process was not in any way damaged, at a time when anything that was said by me or anybody in the White House would immediately be seen through a partisan lens," he said.
Obama also issued his fiercest warning shot for President-elect Trump about embracing illiberal politics.
"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. Or discriminate against people because of their faith or what they look like," he said.
Republicans were unimpressed by Obama's efforts to dial back tensions, with Senator Ben Sasse accusing Obama of a "mere scolding of dictators."
"Instead of President Obama's vague 'we can do stuff,' Congress should debate upending Putin's calculus with a full menu of diplomatic, economic, military, and cyber responses," Sasse said.