However, New York Times says that the privilege of the United States president is not absolute and that the Supreme Court could have stopped him in his tracks despite the conversation between the President and his staff being confidential.
The White House has denied that the conversation with Comey took place as described in the alleged memo, but have offered no further clarification.
The timing of Comey's firing, as the Federal Bureau of Investigation probes possible collusion between Trump's presidential campaign team and Moscow officials, as well as Russia's attempts to influence the election, has stirred controversy, even among some members of Trump's party.
Comey's highly anticipated testimony will be the first time he has made public comments since being terminated as director last month. Just days after Trump's inauguration, he invited the director to dinner and, according to people familiar with Comey's account, asked him repeatedly for his loyalty, which Comey declined to give.
Trump, meanwhile, reportedly told Russian officials in an Oval Office meeting that Comey was a "nut job" and that his dismissal would help get the Russia issue behind him. If Comey wants to tell his story, it will be told - one way or another.
Trump will not block ex-FBI chief Comey's testimony: White House
Things deteriorated thereafter. Trump asked Comey to stop a probe into Michael Flynn case - he stood accused of provided misleading accounts of a phone call with Russia's ambassador.
He may also be unwilling to offer much clarity on the status of the Russian Federation investigation itself up to the point of his departure from the FBI, given legal considerations and the fact that key evidence is likely to be classified.
Should Comey deliver devastating testimony on any of those questions that suggests Trump obstructed justice, he will significantly worsen the political challenges facing the President.
President Donald Trump speaks in the East Room at the White House in Washington, Monday, June 5, 2017.
Spicer said he hadn't spoken to the White House counsel, Don McGahn, about the matter.