Two US intelligence chiefs are set to testify before Congress about possible links between Russia and President Donald Trump’s election campaign.
They will also address Mr Trump’s unsubstantiated claim that he was wiretapped by predecessor Barack Obama.
FBI director James Comey and NSA chief Admiral Mike Rogers will give evidence at a rare open hearing of the congressional intelligence committee.
Mr Trump has called the investigation a “total witch hunt”.
Russia denies attempting to influence the US presidential election.
In January, US intelligence agencies said Kremlin-backed hackers had broken into the email accounts of senior Democrats and released embarrassing ones in order to help Mr Trump defeat Hillary Clinton.
A report by the CIA, FBI and National Security Agency (NSA) said Russian leader Vladimir Putin “ordered” a campaign aimed at influencing the election.
Since then, Mr Trump has faced allegations that his campaign team had links to Russian officials.
