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.