Donald Trump asserted Friday that hacking by foreign powers did not sway the US election, after being briefed on an intelligence report pinning blame on Russia's Vladimir Putin for a cyber-campaign to keep Hillary Clinton out of the White House.

After weeks of rejecting the intelligence community's conclusion that Russia interfered in the election, the president-elect accepted the possibility that Moscow was involved in hacking US targets including the Democratic National Committee.

In a statement after meeting four top intelligence chiefs, Trump acknowledged that cyberattacks by Russia, China and other countries threaten US institutions, political parties, and businesses.

But there was no direct acceptance of the intelligence chiefs' conclusion that Moscow staged an unprecedented attempt to influence the 2016 White House race by hacking and leaking documents that, they said in a new report, also aimed to boost Trump's campaign.

"While Russia, China, other countries, outside groups and people are consistently trying to break through the cyber infrastructure of our governmental institutions, businesses and organizations including the Democrat National Committee, there was absolutely no effect on the outcome of the election," Trump said in a statement.

Trump met the heads of the Directorate of National Intelligence, the Central Intelligence Agency, the Federal Bureau of Investigation and the National Security Agency in New York Friday on their newly completed report into Moscow's alleged interference.

A shortened, declassified version of the report -- released to the public by the Director of National Intelligence shortly after the meeting -- said Putin personally ordered a campaign of hacking and media manipulation to undermine the Democrat Clinton, who had widely been expected to win the November 8 election.

"Russia's goals were to undermine public faith in the US democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency. We further assess Putin and the Russian Government developed a clear preference for President-elect Trump," they said.

The report offered little new evidence on how US intelligence bodies reached their conclusion, and Russia has denied any election meddling.

President Barack Obama had already taken retaliatory action on December 29, expelling 35 Russians he said were intelligence operatives, and placing sanctions on a number of other Russian officials and entities.

Trump's meeting with intelligence chiefs, which the Republican called "constructive," may have smoothed over ruffled feelings between the intelligence bureaucracy and an incoming president who has openly questioned its work.

Just before the meeting, Trump branded the focus on Russia a "political witch hunt" in an interview with the New York Times.

But afterwards Trump said that as soon as he takes office on January 20 he will give a team 90 days to come up with a plan to halt cyberattacks.

"Whether it is our government, organizations, associations or businesses we need to aggressively combat and stop cyberattacks," he said.

The much-anticipated report was likely to further raise the sensitivity over the outcome of an election in which Clinton easily won the popular vote but was beaten by Trump in the electoral college, which decides the winner.

"We must also be clear that there is no evidence that there was any interference in the voting or balloting process," said House Speaker Paul Ryan in a statement.

"We cannot allow partisans to exploit this report in an attempt to delegitimize the president-elect's victory. Donald Trump won this election fair and square because he heard the voices of Americans who felt forgotten."

Republican Senator Lindsey Graham, a strong critic of Trump's dismissal of intelligence conclusions on Russia, also argued there was nothing in the report to indicate an impact on the election outcome.

"I agree with President-elect Trump that Russian cyberattacks did not affect the vote tally and were not responsible for the outcome," Graham said in a statement.

However, Democratic Representative Adam Schiff rejected that conclusion.

"The president-elect's statement that the Russian hacking had 'absolutely no effect on the outcome of the election' is not supported by the briefing, report or common sense," he said. (AFP)