President Donald Trump on Sunday repeated his demand that the identity of the infamous whistleblower whose complaint sparked the House’s impeachment inquiry be disclosed, and even threatened to reveal the person’s name himself.

Trump also attacked the whistleblower’s credibility and claimed without evidence that he has ties to people in President Barack Obama‘s administration like former national security adviser Susan Rice and former CIA director John Brennan. Trump’s latest remarks came on the same day top-ranking Democrats pledged to start unveiling major findings of their impeachment probe, and as several polls show growing support for removing him from office.

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“There have have been stories written about a certain individual, a male, and they say he’s the whistleblower,” Trump told reporters outside the White House. “If he’s the whistleblower, he has no credibility because he’s a Brennan guy, he’s a Susan Rice guy, he’s an Obama guy. And he hates Trump.”

“Now, maybe it’s not him. But if it’s him, you guys ought to release the information,” he added.

The New York Times reported in September that the whistleblower is a CIA officer who was previously detailed to the White House, although it did not confirm whether he worked under Obama.

Democrats on the House Intelligence Committee said last month they would consider having the whistleblower testify in disguise or behind a screen in order to protect his identity. This followed several tweets from Trump in which he said he “deserved” to meet the unnamed agent.

Trump also said Monday on Twitter that he would find it unacceptable if the whistleblower was allowed to submit written answers for his testimony to Congress instead of appearing in person.

The president’s comments are especially significant because he himself refused to sit down for an interview with former special counsel Robert Mueller over the course of the probe into Russian meddling in the 2016 election. Instead, Trump simply submitted written answers to questions.