U.S. Director of National Intelligence James Clapper said on Thursday that Russia has a "long history" of interfering in elections, but that U.S. officials had never encountered activity like its efforts during the 2016 U.S. campaign.
"The Russians have a long history of interfering in elections. Theirs and other people's... This goes back to the 60s, from the heyday of the Cold War," he testified to the Senate Armed Services Committee.
However, he added, "I don't think we've ever encountered a more aggressive or direct campaign to interfere in our election process than we've seen in this case." (Reporting by Patricia Zengerle and Dustin Volz; Editing by Chizu Nomiyama)
Below is an earlier reported version from Reuters:
Russian cyber attacks pose a "major threat" to the United States, top U.S. 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 Trump called himiself 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 lawmakers are wary of Moscow and distrust Trump's praise of Russian President Vladimir Putin and efforts to heal the rift between the United States and Russia.
Trump, who becomes the U.S. president on Jan. 20, 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 U.S. interests because of its "highly-advanced offensive cyber program" and sophisticated capabilities.
"Russia is a full-scope cyber actor that poses a major threat to U.S. government, military, diplomatic, commercial and critical infrastructure," they said in a joint statement.
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 U.S. political groups in the 2016 election.
U.S. intelligence agencies say Russia was behind hacks into Democratic Party organizations and operatives before the election, a conclusion supported by several private cybersecurity firms. Moscow denies the hacking allegations.
U.S. intelligence officials have said the Russian cyber attacks were aimed at helping Trump defeat Democrat Hillary Clinton in the Nov. 8 election.
Several Republicans have acknowledged the Russian hacking but have not linked it to an effort to help 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, 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, Trump said in another post on Twitter that he was not against intelligence agencies or in agreement with Assange, whose organization leaked Democrats' emails.
"The media lies to make it look like I am against 'Intelligence' when in fact I am a big fan!" Trump wrote.
Trump and top advisers believe Democrats are trying to delegitimize his election victory by accusing Russia of helping him.
An unclassified version of the intelligence community's review of Russian interference in the U.S. election will be made public early next week and will assign a motive for the attacks, Clapper said. The report was delivered to President Barack 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 U.S. diplomats.
Some lawmakers, including 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 U.S. elections.
Clapper declined to say whether cyber attacks of the nature carried out during the election consituted an act of war. That determination would be a "very heavy policy call," said Clapper, the country's top intelligence official.
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.
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 Tillerson was Exxon Mobil chief executive.
McCain asked Clapper whether he believed WikiLeaks' Assange had put U.S. lives in direct danger. He said he agreed. Clapper also said he did not think Assange had any credibility.
Clapper was also asked about some media reports that authorities are considering a reorganization of the U.S. intelligence community. He said he has not been involved in any conversations about restructuring. (By Dustin Volz and Patricia Zengerle; Additional reporting by Patricia Zengerle and Mark Hosenball in Washington; Editing by Bernadette Baum and Alistair Bell)