President Donald Trump says he has spoken to the US attorney general about tracing the origins of the inquiry that cleared him of colluding with Russia.
Mr Trump described the investigation by former FBI director Robert Mueller as “an attempted coup”.
Attorney General William Barr meanwhile told lawmakers he believes the Trump campaign was spied on by the FBI.
US intelligence officials have previously said they were spying on the Russians, not the Trump campaign.
Speaking to reporters at the White House on Wednesday morning, the Republican president railed against the Department of Justice inquiry into whether the Trump campaign had conspired with the Kremlin to sway the 2016 election.
The investigation cleared him and his aides of collusion, making no determination on whether they had tried to obstruct justice.