Russian President Vladimir Putin sought to help Donald Trump win the presidential election, a US intelligence report says.
The unclassified report says the Russian leader “ordered” a campaign aimed at influencing the election.
Moscow has not commented, but Russia has previously denied the claims.
After being briefed on the findings, Mr Trump stopped short of accusing Russia of interfering, saying only that the election outcome was not affected.
Mr Trump later went on to blame “gross negligence” by the Democratic National Committee for “allowing” the hacking to take place.
Following the report’s findings, the US Department of Homeland Security announced that voting machines and other election databases would be classified as “critical infrastructure” and given more protection from cyber-attack.
The 25-page report says that the Kremlin developed a “clear preference” for Mr Trump.
Russia’s goals, the document added, were to “undermine public faith” in the US democratic process and “denigrate” his Democrat opponent Hillary Clinton, harming her electability and potential presidency.
“We assess Russian President Vladimir Putin ordered an influence campaign in 2016 aimed at the US presidential election,” it said.
The report says Mr Putin liked Mr Trump because he had vowed to work with Russia and the Russian leader had had “many positive experiences working with Western political leaders whose business interests made them more disposed to deal with Russia, such as former Italian Prime Minister Silvio Berlusconi and former German Chancellor Gerhard Schroeder”.
In contrast, Mr Putin had blamed Mrs Clinton for inciting anti-government protests in 2011 and early 2012 “and because he holds a grudge for comments he almost certainly saw as disparaging him”.
The identities of the Russian agents allegedly directly responsible for the hack are known to US authorities but have not been released publicly, reports say, citing intelligence sources.
The document, a cut-down version of the classified report presented to President Barack Obama on Thursday, was released shortly after intelligence chiefs briefed Mr Trump on their findings.
Since winning the election on 8 November, Mr Trump has repeatedly questioned US intelligence claims of Russian hacking. In a statement after the briefing, the president-elect declined to single out Russia, but said he had “tremendous respect for the work and service done” by those in the US intelligence community.
“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 said.
“Whether it is our government, organisations, associations or businesses we need to aggressively combat and stop cyber-attacks. I will appoint a team to give me a plan within 90 days of taking office.”
