Washington (CNN) Senate Judiciary Chairman Lindsey Graham asserted Sunday that the impeachment inquiry into President Donald Trump is "invalid" unless the identity of the anonymous whistleblower whose complaint sparked House Democrats' probe is revealed.

Graham, whose committee would be at the center of Trump's trial in the Senate should the House approve articles of impeachment against the President, also said in his Sunday interview with Fox News that the process would be "dead on arrival" in the Republican-controlled chamber if the whistleblower doesn't testify before Congress.

"I consider any impeachment in the House that doesn't allow us to know who the whistleblower is to be invalid because without the whistleblower complaint, we wouldn't be talking about any of this and I also see the need for Hunter Biden to be called to adequately defend the President and if you don't do those two things it's a complete joke," Graham, a South Carolina Republican, said.

He continued: "It's impossible to bring this case forward in my view fairly without us knowing who the whistleblower is and having a chance to cross examine them about any biases they may have. So if they don't call the whistleblower in the House, this thing is dead on arrival in the Senate."

CNN has reached out to Graham for clarification on what he means by "invalid."