WASHINGTON (BLOOMBERG) - United States President Donald Trump slammed James Comey in a tweet, days after the fired FBI director's testimony to the Senate Intelligence Committee.

The latest tweet came as Attorney-General Jeff Sessions prepares to speak to the same panel to answer questions about alleged Russian meddling in the 2016 presidential election.

"I believe the James Comey leaks will be far more prevalent than anyone ever thought possible. Totally illegal? Very 'cowardly!'" Trump told his 32 million Twitter followers on Sunday (June 11).

On Friday, Trump said during a news conference at the White House that Comey's Senate testimony a day earlier showed that the president hadn't colluded with the Russian government to rig the 2016 election and hadn't obstructed a federal investigation into the meddling.

Trump also said he would "100 per cent" be willing to testify under oath that he didn't demand a pledge of personal loyalty from Comey.

Sessions on Saturday agreed to switch planned appearances at a pair of appropriations panels on Tuesday and instead appear before the intelligence committee.

The committee has not announced the timing of the event, or whether Sessions will speak in an open or closed hearing.

Appropriate Forum In letters Saturday to Senator Richard Shelby, Republican of Alabama, and Representative John Culberson, Republican of Texas, Sessions said he'd concluded that regardless of which committees he appeared before, the questions would inevitably focus on the Russian probe.

Following Comey's testimony, "it is important that I have the opportunity to address these matters in the appropriate forum", Sessions wrote to Shelby, who chairs the Senate appropriations panel he was scheduled to address.

Members of the intelligence committee are in the middle of an investigation and have "access to relevant, classified information", Sessions said.

Deputy Attorney General Rod Rosenstein will stand in for Sessions at the appropriations subcommittee hearings on Tuesday.