In a separate letter to Mr. Nunes obtained by CNN, Mr. Schiff said that the anonymous person "has a right under laws championed by this committee to remain anonymous and to be protected from harm". So far, they say, they have not received one.
"Crickets", said Mark Zaid, an attorney for the whistleblower. Zaid said that until Nunes formally declines the offer, it will continue to stand.
Nunes' office did not respond to requests for comment on Sunday.
(AP) Democrats must approve any requests submitted by Republicans and they are expected to reject the requests for Hunter Biden and the whistleblower to appear.
"The whistleblower's testimony is therefore redundant and unneccessary", Schiff said.
Rep. Will Hurd of Texas, who has broken with the White House on other issues, said Sunday the whistleblower should not have been included on a list of witnesses the Republicans wanted to testify in open hearings set to begin Wednesday.
"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", he said. "So you have direct evidence, not indirect evidence".
She added, "And the whistleblower has great risk associated with his life right now".
On "Fox News Sunday", Rep. Lindsey Graham says we need to know what the background is of the whistleblower.
President Trump on Sunday called on Republicans to fully support his "perfect" Ukraine call and not just attack the impeachment inquiry. On ABC's "This Week," Rep. Mac Thornberry (R-Texas), said that although Trump's behavior might have been inappropriate, "I do not believe it was impeachable".
He added, however, "I do not believe it was impeachable".
"When you find out who is the whistleblower is, I'm confident, you're gonna find out it's somebody from the deep state". John Kennedy of Louisiana, said the president's behavior may have crossed the line.
"You can't limit the witnesses", Kennedy said. Rand Paul, R-Ky., argued that "it's unfair to treat Trump under one standard and Joe Biden under a different standard".
"Presidents have withheld aid before for corruption", Paul said on NBC's Meet the Press . "I think this is a bunch of B.S".
But Democrats maintain that President Trump's attempts to enlist a foreign power to dig up dirt on a political rival in order to help his re-election bid was an abuse of power.
On Friday Marie Yovanovitch, the former USA ambassador to Ukraine, is scheduled to testify.