Russian cyberattacks pose a "major threat" to the country, top US intelligence officials told a congressional hearing on Thursday despite skepticism from president-elect Donald Trump about findings that Moscow orchestrated hacking of the 2016 election.
Although Mr Trump called himself a "big fan" of the intelligence community on Thursday, he is heading for a conflict over the issue with Democrats and some fellow Republicans in Congress.
Many politicians are wary of Moscow and distrust Mr Trump's praise of Russian president Vladimir Putin and efforts to heal the rift between the US and Russia.
Mr Trump, who becomes the US president on January 20th, will be briefed by intelligence agency chiefs on Friday on hacks that targeted the Democratic Party during the presidential election campaign that he won.
Director of National Intelligence James Clapper, National Security Agency Director Mike Rogers and Undersecretary of Defense for Intelligence Marcel Lettre testified on Thursday before the Senate Armed Services Committee, which is chaired by Republican John McCain, a vocal critic of Putin.
The intelligence officials described Moscow as a major threat to a wide range of US interests because of its “highly-advanced offensive cyberprogram” and sophisticated capabilities.
“Russia is a full-scope cyberactor that poses a major threat to US government, military, diplomatic, commercial and critical infrastructure,” they said in a joint statement.
President Barack Obama last week ordered the expulsion of 35 Russian suspected spies and imposed sanctions on two Russian intelligence agencies over their alleged involvement in hacking US political groups in the 2016 election.
US intelligence agencies say Russia was behind hacks into Democratic Party organisations and operatives before the election, a conclusion supported by several private cybersecurity firms. Moscow denies the hacking allegations.
US intelligence officials have said the Russian cyberattacks were aimed at helping Mr Trump defeat Hillary Clinton in the November 8th election.
Several Republicans have acknowledged the Russian hacking but have not linked it to an effort to help Mr Trump win.
Documents stolen from the Democratic National Committee and Clinton campaign chairman John Podesta were leaked to the media in advance of the election, embarrassing the Clinton campaign.
In a tweet on Wednesday, Mr Trump cast doubt on a Russian role in the affair, writing: "[WikiLeaks founder] Julian Assange said 'a 14 year old could have hacked Podesta' – why was DNC so careless? Also said the Russians did not give him the info!"
However, on Thursday, Mr Trump said in another post on Twitter that he was not against intelligence agencies or in agreement with Mr Assange, whose organisation leaked Democrats’ emails.
“The media lies to make it look like I am against ‘Intelligence’ when in fact I am a big fan!” Mr Trump wrote.
Mr Trump and top advisers believe Democrats are trying to delegitimise his election victory by accusing Russia of helping him.
An unclassified version of the intelligence community’s review of Russian interference in the US election will be made public early next week and will assign a motive for the attacks, Mr Clapper said. The report was delivered to Mr Obama on Thursday, he said.
In the afternoon, State Department and Department of Homeland Security officials will brief the Senate Foreign Relations Committee behind closed doors on the Obama administration's response to the hacking and harassment of US diplomats.
Some lawmakers, including Mr McCain, said a firmer response was needed to check Russian aggression in cyberspace and elsewhere, and to discourage other countries from trying to influence more US elections.
Mr Clapper declined to say whether cyberattacks of the nature carried out during the election constituted an act of war. That determination would be a “very heavy policy call,” said Mr Clapper, the country’s top intelligence official.
Mr McCain is among a handful of Republicans to join Democrats in pushing for a special committee to investigate Russia’s political hacking, although that effort faces opposition from Republican leaders in Congress.
Mr Trump has nominated people seen as friendly toward Moscow to senior administration posts, including secretary of state nominee Rex Tillerson, who was awarded Russia's "Order of Friendship" in 2013 while Mr Tillerson was Exxon Mobil chief executive.
Mr McCain asked Mr Clapper whether he believed WikiLeaks had put US lives in direct danger. He said he agreed. Mr Clapper also said he did not think Mr Assange had any credibility.
Mr Clapper was also asked about some media reports that authorities are considering a reorganisation of the US intelligence community. He said he has not been involved in any conversations about restructuring.