In a taste of the briefing President-elect Donald Trump will get on Friday from top US intelligence officials, America's top spy told Senators that Russia continues to assail the country with propaganda, disinformation and fake news.

"They did not change any vote tallies or anything of that sort," Director of National Intelligence, James Clapper, told the Senate Armed Services Committee about Russian influence on the 2016 election on Thursday (5 January). But the "totality" of what Russia did, Clapper said, is "a great concern."

In October, Clapper's office issued a statement laying blame on Russia for hacking and theft of emails from the Democratic National Committee (DNC) and later a breach of the Democratic campaign in the spring and summer. The internal emails of both groups, American intelligence agencies have concluded, were leaked by WikiLeaks throughout the later days of the 2016 election campaign.

The intelligence agencies "have no way of gauging the impact it had on the choices that the electorate made," Clapper said. Whether the hacking "constitutes an act of war is a very heavy policy call." But he said the US has never "encountered a more aggressive campaign to interfere in our election process."

Clapper said that Russia disparaged American democracy and picked at US "hypocrisy about human rights" and looked for "whatever crack of fissure in our tapestry, if you will, they could exploit." This included using Russian media outlet RT, social media and fake news, in "addition to the hacking" to influence the election, he said. Their efforts had "more than one motive," he added.

Clapper was joined in giving testimony by Cyber Command Chief Admiral Mike Rogers, and Defense Undersecretary Marcel Lettre.

Three versions of the much-anticipated intelligence report into Russian hacking operations against US political targets during the election are being compiled, with a declassified copy set to be released into the public domain next Monday (9 January).

"I intend to push the envelope as much as I can on the unclassified version," Clapper said. "The public should know as much about this as possible." But he said that the intelligence agencies won't be able to provide all their evidence as "there are some sensitive sources and methods." He said the report "will ascribe a motivation" to Russian influence, but did not go into detail as "I don't want to pre-empt our report," he said.

Clapper and the heads of the CIA and FBI are set to brief Trump on their findings on Friday (6 January). On Wednesday (4 January) Trump officials said that "the intelligence world has become completely politicised" amidst news that the President-elect is looking to overhaul the CIA and the Office of the Director of National Intelligence and slim them down.

Trump has repeatedly expressed his doubt that Russia hacked the Democrats or had any influence on the election and questions the accuracy of intelligence agency findings.