Trump says the whistleblower is a 'radical'
Trump also said, without providing evidence, the whistleblower is "an Obama guy" who "hates Trump."
He categorized the Democrats as working for the "fake media" - who he claimed are the only ones who want to see him impeached.
Trump's comments on Sunday came on the heels of the whistleblower's attorney, Mark Zaid, saying his client would answer questions directly to Republicans on the intelligence committee leading the impeachment inquiry.
Zaid's offer is an effort to counter Republican attempts, led by Trump, to unmask the whistleblower, a member of the U.S. intelligence community whose identity has not been released.
