Former FBI Director James Comey's prepared statement to Congress establishes that Donald Trump obstructed justice, a senior legal analyst has claimed.

Mr Comey is set to testify in an open hearing before the Senate Intelligence Committee, where he is expected to disclose new details about whether Mr Trump attempted to pressure him into dropping an investigation into former National Security Adviser Michael Flynn.

Mr Flynn resigned in February after it was revealed that he had misled Vice President Mike Pence and other White House officials about his conversations with a Russian official.

Mr Trump told him that "Flynn hadn’t done anything wrong on his calls with the Russians, but had misled the Vice President,", Mr Comey said in his opening statement.

"He then said: 'I hope you can see your way clear to letting this go, to letting Flynn go. He is a good guy. I hope you can let this go.'"

Jeffrey Toobin, a former counsel with the Department of Justice and current legal analyst, tweeted that "Comey's statement establishes obstruction of justice by Trump. Period."

"[Flynn] gets fired. He’s under criminal investigation," Mr Toobin said in a separate interview with CNN. "And the president brings in the FBI Director and says 'please stop your investigation.' If that isn’t obstruction of justice, I don’t know what is."

Mr Comey’s remarks echoed a memo he had written about his interaction with the president, which was described to various news outlets.