Washington (CNN) President Barack Obama on Friday all but named Russian President Vladimir Putin as behind Moscow's alleged attempts to meddle in the US election, vowing retaliation for the moves and defending himself against criticism his administration acted too slowly.

Without directly answering whether Putin ordered up the cyberactivity that US intelligence says was meant to bolster Donald Trump, Obama described government in Russia as tightly controlled by the man at the top.

"Not much happens in Russia without Vladimir Putin," he said. "This happened at the highest levels of the Russian government."

Obama said he personally confronted Putin about the hacking in September on the sidelines of the Group of 20 summit in China, telling the Russian leader to "cut it out" and warned of "serious consequences if he didn't."

"In fact, we did not see further tampering of the election process," Obama said of the aftermath of that conversation. "But the leaks through WikiLeaks had already occurred."

Obama, however, did not say whether he has addressed with Putin Russian's post-election hacking activity which has continued largely unabated, US officials briefed on the investigation this week told CNN.

The outgoing President's year-end press conference was dominated by questions about Russia and its influence in last month's vote.

After unleashing a string of putdowns about Russia, describing America's Cold War adversary as "a weaker country" that "doesn't produce anything anyone wants to buy except oil and gas and arms," Obama conceded the country could exploit political divisions in the United States.

"They can impact us if we lose track of who we are. They can impact us if we abandon our values," Obama said.

He attacked Republicans for siding with an arch-enemy of the United States because of their dislike of Democrats.

"Ronald Reagan would roll over in his grave," Obama said of recent GOP praise of Russia.

He warned, "Mr. Putin can weaken us just like he is trying to weaken Europe if we start buying into notions that it is okay to intimidate the press or lock up dissidents."

Obama's given Trump advice

Referring the relationship between his White House and the incoming Trump administration, Obama said Friday there was no "squabbling" between the sides, even amid a roiling debate over Russia's intrusion into the US election.

The President noted he had made "some pretty specific suggestions" to successor Donald Trump about "maintaining the effectiveness, integrity, cohesion of the office," he said during his news conference Friday.

"He has listened," Obama said. "I can't say that he will end up implementing, but the conversations themselves have been cordial as opposed to defensive in any way."

Obama said he would "always make myself available to him" during his tenure for counsel and advice.

On the alleged Russia hacks, he said the issue should be confronted on a bipartisan basis.

"What we have simply said are the facts," Obama said. "Based on uniform intelligence assessments, the Russians were responsible for hacking the DNC, and as a consequence, it is important for us to review all elements of that and make sure we are preventing that kind of interference through cyberattacks in the future."

"That shouldn't be a partisan issue," Obama went on. "My hope is the President-elect is similarly going to be concerned that we don't have foreign influence in our election process."

Despite his assurances, his White House has increasingly been engaged in an escalating rift with Trump's transition team over Moscow's intrusion into the US vote. At the same time, Obama is working to foster a productive relationship with his successor in a bid to influence his presidential decision-making.

Promised response to Moscow

Some Democrats have argued the White House was slow in naming Russia as the hacking culprit, though Obama and his aides argue that pushing the intelligence community to make that assessment earlier would have appeared like political interference.

In an interview with NPR that aired Friday , Obama attempted a balance, saying it was clear Trump and his team knew what Russia's intentions were, but arguing the issue shouldn't become mired in partisan politics.

"It requires us not to re-litigate the election, it requires us not to point fingers, it requires us to just say, here's what happened, let's be honest about it, and let's not use it as a political football but let's figure out how to prevent it from happening in the future," Obama said.

He said Trump would be wise to uphold a US commitment to international norms.

"I had a conversation with the President-elect about our foreign policy generally, and the importance of us making sure that in how we approach intelligence gathering and how we think about fighting terrorism and keeping the country secure ... that we recognize America's exceptionalism, our indispensability in the world in part draws from our values and our ideals," Obama said.

On Friday, he said that Russia's cyber meddling "was not some elaborate complicated espionage scheme," arguing instead that a hyperpartisan political environment led to an obsession with leaked emails.

"I'm finding it curious that everybody is suddenly acting surprised that this looked like disadvantaging Hillary Clinton because you guys wrote about it everyday," Obama said. "This was an obsession that dominated the news coverage."

Overall, Obama contended, Clinton was "treated unfairly" in the presidential contest.

"I think the coverage of her and the issues was troubling," Obama said.

Criticism of Syria

It comes as Obama also finds himself reckoning with a worsening humanitarian emergency in Syria , where Russian and Iranian-backed government forces recently retook the city of Aleppo. Obama has called Syria a deeply frustrating crisis that haunts him daily.

He condemned the situation Friday, harshly accusing the Syrian regime, along with Moscow and Tehran, of slaughtering civilians in Aleppo.

"We have seen a deliberate strategy of surrounding, besieging and starving innocent civilians," Obama said.

"Responsibility for this brutality lies in one place alone: the Assad regime and its allies Russia and Iran," Obama declared. "The blood for these atrocities are on their hands."

On China, where Trump has called for a different course, Obama said it was "fine" to reexamine the longstanding "One China"

, which spells US recognition of Taiwan as a part of China.

But Obama said it was essential Trump familiarize himself with the consequences of his moves, saying his team should be briefed by current officials.

"What I have advised the President-elect is that across the board on foreign policy, you want to make sure that you're doing it in a systematic, deliberate, intentional way," Obama said. "He should want his team to be fully briefed on what's gone on in the past and where the potential pitfalls may be, where the opportunities are, what we've learned from eight years of experience.

The President led off the traditional Q-and-A session by touting his achievements from his time in office, starting off by noting that Thursday saw the biggest number of Obamacare sign-ups -- 670,000 people -- in a single day.

A spokesman for the Department of Health and Human Services said that it was due to this "extraordinary demand" that the deadline to sign up for coverage beginning on January 1, 2017, has been extended until December 19.

The news comes just weeks ahead of lawmakers reconvening for the new session of Congress on January 3. Republicans intend to move swiftly to repeal major parts of the Affordable Care Act through a budget reconciliation bill.