President-elect Donald Trump, after a briefing Friday from the country's top intelligence officials, said that hacking had "absolutely no effect" on the outcome of November's election.
Trump also said he would ask for a plan within 90 days of taking office on how to "aggressively combat and stop cyberattacks."
Before seeing the intelligence, Trump had dismissed the findings and told The New York Times the focus on Russia's involvement is a "political witch hunt" by adversaries who are embarrassed they lost the election.
"They got beaten very badly in the election," Trump told the Times. "They are very embarrassed about it. To some extent, it's a witch hunt. They just focus on this."
The declassified report, released Friday, said Putin "ordered" an influence campaign in 2016 aimed at the U.S. presidential election.
U.S. intelligence officials released the 25-page public version of the report Friday, after they briefed Trump and top lawmakers on Capitol Hill from a longer, classified version.
The report says Russian efforts to influence the 2016 presidential election represent the most recent expression of Moscow's long-standing desire to undermine the U.S.-led liberal democratic order. It says the scope of Russia's activities was significantly larger compared with previous operations.
House Minority Leader Nancy Pelosi, D-Calif., said the intelligence report was "quite a stunning disclosure."
Upset that NBC released information about the hacking, Trump tweeted: "I am asking the chairs of the House and Senate committees to investigate top secret intelligence shared with NBC prior to me seeing it." NBC reported that intelligence officials have identified proxies that Russia used to pass hacked Democratic emails to WikiLeaks, which then released them to the public.
Since winning the election, Trump has repeatedly questioned intelligence officials' assessments that Russia was behind the hacking of the Democratic National Committee and individual Democrats like Hillary Clinton campaign chairman John Podesta.
Trump remained dubious about the assertion even on the eve of his intelligence briefing, asking how officials could be "so sure" about the hacking if they had not examined DNC servers.
"What is going on?" he wrote on Twitter.
A senior law enforcement official said the FBI repeatedly stressed to DNC officials the importance of obtaining direct access to the servers "only to be rebuffed until well after the initial compromise had been mitigated." The official said the FBI had to rely on a "third party" for information, but did get access to the material it needed.
The Washington Post, citing anonymous U.S. officials, reported Thursday that intelligence agencies have identified parties who delivered stolen Democratic emails to WikiLeaks. The officials also said there were disparities between efforts to infiltrate Democratic and Republican networks, and said the U.S. intercepted communications in which Russian officials celebrated Trump's victory. It was not clear which of those details were included in the classified report.
Former CIA Director Leon Panetta said on NBC's "Today" show Friday that once Trump is briefed by intelligence officials about alleged Russian hacking, he “is going to realize that this is a very important issue that must be dealt with seriously.”
He said Trump's distrust of the intelligence community is something Americans have to be concerned about and something he's never encountered before from an incoming or sitting president.
"I've been in public service for over 50 years," Panetta said. "I have never seen anything like this in my lifetime."