President Obama, in a freewheeling final press conference of the year, blasted Syria for trying to “slaughter its way to legitimacy," Russia for meddling in the U.S. elections, and even some Donald Trump supporters, who he said would make "Ronald Reagan roll over in his grave” for warming to Vladimir Putin.

Though he had strong words for Russia, Obama stopped short of saying Putin himself orchestrated the Russian hacking of U.S. political sites during the election – but he did say it was done at the highest levels of the Kremlin.

He says he will let the public decide whether there were rogue high-level Russian officials acting without Putin's knowledge.

Obama also urged Trump to back a bipartisan investigation into the matter.

"Not much happens in Russia without Vladimir Putin," Obama said in his year-end news conference. The president said he had warned Putin there would be serious consequences it he did not "cut it out," through Obama did not specify the extent or timing of any U.S. retaliation.

Democrat Hillary Clinton has even more directly cited Russian interference. She said Thursday night, "Vladimir Putin himself directed the covert cyberattacks against our electoral system, against our democracy, apparently because he has a personal beef against me."

Obama did not publicly support that theory Friday. He did, however, chide the media for that he called an "obsession" with the flood of hacked Democratic emails that were made public during the election's final stretch.

U.S. intelligence assessments that Russia interfered in the election to benefit Trump have heightened the already tense relationship between Washington and Moscow.

In the wide ranging press conference, Obama rejected the notion that the dispute over the origin of the hacking was disrupting efforts to smoothly transfer power to Trump. Despite fiercely criticizing each other during the election, Obama and Trump have spoken multiple times since the campaign ended.

"He has listened," Obama said of Trump. "I can't say he will end up implementing. But the conversations themselves have been cordial."

Trump's election has upended the Democratic Party, which expected to not only win the White House but also carry the Senate. Instead, the party finds itself out of power on both ends of Pennsylvania Avenue.

In a moment of self-reflection, Obama acknowledged that he had not been able to transfer his own popularity and electoral success to other sin his party.

"It is not something that I've been able to transfer to candidates in midterms or build a sustaining organization around," Obama said. "That's something I would have liked to have done more of but it's kind of hard to do when you're dealing with a whole bunch of issues here in the White House."

Separately, Obama blamed Russia for standing in the way of international efforts to stop the civil war in Syria, where government forces have beaten back rebels in their stronghold of Aleppo.

Obama strongly condemned the actions of the Syrian regime, declaring it could not “slaughter its way to legitimacy” and calling for an international observer force in Aleppo.

“The world shall not be fooled, and the world will not forget,” Obama said.

Obama began his press conference by touting his achievements from his time in office, noting that the unemployment rate has decreased and higher rates of insured people under his healthcare overhaul.

Obama said he was leaving the country "stronger and more prosperous than it was when we started."

Following Friday’s press conference, Obama departed for his annual family vacation in Hawaii.

The Associated Press contributed to this report.