The Russian leader "aspired to help" Donald Trump, a report claims, but the President-elect turns the blame on the Democrats.
Vladimir Putin ordered a campaign to influence the US presidential election, according to a newly declassified report by American spy chiefs.
The Russian leader and his government "aspired to help" Donald Trump's chances of winning by discrediting his rival Hillary Clinton, it is claimed.
Mr Trump unexpectedly beat Mrs Clinton in the election, but he has been sceptical of accusations that Moscow was behind a hacking campaign that sought to boost his chances.
He tweeted: "Gross negligence by the Democratic National Committee allowed hacking to take place. The Republican National Committee had strong defense!"
The report from the director of national intelligence, James Clapper, said: "We assess Russian President Vladimir Putin ordered an influence campaign in 2016 aimed at the US presidential election.
"Russia's goals were to undermine public faith in the US democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency."
Mr Putin most likely wanted to discredit Mrs Clinton because he blames her for inciting protests against his regime in late 2011 and early 2012, and because he resents her for disparaging comments she has made about him, the report said.
The report said Russian intelligence accessed "elements" of multiple state and local electoral boards, but "the systems targeted or compromised were not involved in counting votes".
US intelligence agencies also believe Moscow hacked into the emails of the Democratic National Committee and Mrs Clinton's campaign team and fed the material to WikiLeaks.
But the report claimed there were also targets associated with the Republican party.
Before he met spy chiefs for a briefing on the report on Friday, the President-elect dismissed the controversy as a "political witch-hunt".
Later, he said he had "constructive talks" with them and vowed to crack down on hacking.
He said he would appoint a team to "aggressively combat and stop cyber attacks" by coming up with a plan within 90 days of him taking office on 20 January.
It made clear the Russian government had developed a "clear preference for President-elect Donald Trump". of the intelligence officials: "I have tremendous respect for the work and service done by the men and women of this community to our great nation."
He went on: "While Russia, China, other countries, outside groups and people are consistently trying to break through the cyber infrastructure of our governmental institutions, businesses and organisations including the Democrat National Committee, there was absolutely no effect on the outcome of the election."
He also claimed there were unsuccessful attempts to hack into the Republican National Committee.
Russia has denied the US government's hacking claims.
President Barack Obama last week imposed fresh sanctions on Moscow and expelled dozens of diplomats in retaliation.
Meanwhile, Vice President Joe Biden has told Mr Trump to "grow up" as he criticised his "absolutely mindless" attacks on intelligence agencies.
The row between Mr Trump and his spy chiefs "leaves us in a very dark place", according to the former National Security Agency and CIA director, General Michael Hayden.
He told Sky News that intelligence officials made a "high confidence judgement and he (Trump) said 'take a hike'. Wow".
Gen Hayden added: "That is going to reverberate throughout the community."