Senior US intelligence officials face questions at a Senate hearing that will be dominated by the intelligence community's assessment that Russia meddled in the presidential election to help Donald Trump win.

The Armed Services Committee's cyber threats hearing on Thursday comes a day before the president-elect is to be briefed by the CIA and FBI directors along with the director of national intelligence on the investigation into Russia's alleged hacking efforts.

Trump has been deeply critical of their findings, even appearing to back controversial WikiLeaks founder Julian Assange's contention that Russia did not provide him with hacked Democratic emails.

The committee's session is the first in a series aimed at investigating purported Russian cyber-attacks against US interests and developing defenses sturdy enough to blunt future intrusions.

"We will obviously be talking about the hacking, but the main thing is the whole issue of cybersecurity," the committee's Republican chairman, Sen. John McCain of Arizona, said ahead of the hearing. "Right now we have no policy, no strategy to counter cyberattacks." 

Slated to appear before the Armed Services Committee are James Clapper, the national intelligence director; Marcel Lettre, the undersecretary of defense for intelligence; and Michael Rogers, National Security Agency chief and the top officer at the US Cyber Command.

Accusations Russia interfered in the 2016 election by hacking Democratic email accounts have roiled Washington for weeks. President Barack Obama struck back at Moscow in late December with a sweeping set of sanctions targeting Russia's leading spy agencies the GRU and FSB that the US said were involved. The GRU is Russia's military intelligence agency.

The FSB is the main successor to the Soviet-era KGB.

But the sanctions against both Russian intelligence agencies could easily be rescinded by Trump, who has so far publicly refused to accept the conclusion that Russia is responsible for the attacks.

Trump earlier this week escalated his criticism of US intelligence professionals, such as Clapper by tweeting, without evidence, that an upcoming briefing on the suspected Russian hacking had been delayed until Friday, and said, "perhaps more time needed to build a case".

Intelligence officials said there had been no delay.

Trump also suggested on Wednesday in a tweet that one of Russia's primary targets, the Democratic National Committee, could be to blame for being "so careless.