Comey, fired by Trump last month, is due to testify on Thursday before the Senate Intelligence Committee in both an open session and behind closed doors. The hearings could add to problems facing the president over probes into alleged Russian meddling in last year’s U.S. election and potential collusion by his campaign.

In an interview with ABC News, Conway appeared to indicate that the president would allow Comey to testify, saying, “We’ll be watching with the rest of the world when Director Comey testifies.”

But asked directly whether Trump would use executive privilege to prevent Comey from speaking with lawmakers, Conway added: “The president will make that decision.”

Legal experts say Trump could invoke a doctrine called executive privilege to try to stop Comey from testifying. But such a maneuver would likely draw a backlash and could be challenged in court, they said.

Trump fired Comey on May 9, prompting a political firestorm and accusations by critics that he was improperly seeking to hinder an FBI probe into Russia’s role in the election and potential collusion by Trump’s campaign.

Comey is expected to be asked by the Senate panel about conversations in which the president is reported to have pressured him to drop a related FBI investigation into Trump’s former national security adviser Michael Flynn, whose ties to Russia are under scrutiny.

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The Justice Department and several U.S. congressional committees are investigating the Russia matter.

The Russian government has denied U.S. intelligence agencies’ conclusion that it sought to influence the election in Trump’s favor, but Russian President Vladimir Putin said on Thursday that some Russian individuals may have acted on their own.

Trump, who has raised doubts about the U.S. agencies’ findings, has denied any collusion.