President Trump not expected to try to block Comey testimony, aides say The president has no plan to invoke executive privilege.

 -- President Trump has no plans to invoke executive privilege in an attempt to block fired FBI Director Jim Comey from discussing in his testimony before Congress this week any conversations he had with the president, two White House advisers told ABC News.

While the officials stress that Trump could change his mind ahead of Comey's scheduled appearance before the Senate Intelligence Committee on Thursday, they said attempting to block the former FBI chief's testimony would look terrible for the president and would have no guarantee of success legally.

“There’s nothing Comey could say that would be more damaging than trying to silence him," one White House adviser told ABC News.

Another official said it is questionable whether it would even work to invoke executive privilege to prevent the former FBI chief from testifying about his conversations with the president before Trump fired him considering that Comey is now a private citizen and Trump himself has in tweets and interviews discussed details of his private talks with him.

The executive privilege doctrine is “the right of a president to withhold information from those with compulsory power -- including special counsels and congressional committees -- but only when it’s in the public interest to do so,” said Mark Rozell, dean of the Schar School of Policy and Government at George Mason University and author of "Executive Privilege: Presidential Power, Secrecy and Accountability."

Past presidents, including Barack Obama and Bill Clinton, asserted executive privilege in some encounters with Congress. But this presidential privilege is most greatly associated with the Watergate scandal when Richard Nixon tried to block the release of taped recordings of his Oval Office conversations to a special prosecutor.

ABC's Alexander Mallin and Lauren Pearle contributed reporting to this piece.