Josh Hawley, R-Mo., said on “Fox & Friends” on Monday that if witnesses are allowed in President Trump’s Senate impeachment trial, then lead House impeachment manager Adam Schiff, D-Calif., former Vice President Joe Biden and his son Hunter, as well as the whistleblower should all be called to testify.

“If my colleagues and others decide, you know what, we have got to have witnesses, then let's call everybody who is going to be relevant,” said Hawley, who serves on the Senate Judiciary Committee.

“This isn't just about [former national security adviser] John Bolton. This should be about the whistleblower, Adam Schiff, Hunter Biden -- let’s hear from them all.”

Hawley made the comments hours before President Trump's impeachment legal team was expected to resume their defense arguments.

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In the coming days, the Senate is expected to vote on whether Trump’s trial will permit any witnesses. Democrats want to hear from witnesses including Bolton, who said earlier this month that he would testify should he be subpoenaed by the Senate.

Republicans have a wish list, too, if witnesses are necessary at Trump's impeachment trial.

“If the Senate decides to call witnesses later this week, we need to hear from Adam Schiff number one,” Hawley said. “We know his staff had contact with the so-called whistleblower before the whistleblower filed his complaint. We know that Schiff's staff gave the whistleblower direction. I want to know what direction. I want to know what they talked about.”

“By the way, Schiff lied about that. Why did he? I think we ought to find that out,” Hawley continued, adding that Hunter Biden should testify, too, because “he is right at the center of this.”

“What was he doing in Ukraine? What was he doing with Burisma [Holdings]?" the Missouri lawmaker asked. "And probably Joe Biden. What did Joe Biden know when he asked the Ukrainians to fire that prosecutor who was looking into Hunter?”

Hunter Biden served on the board of Burisma Holdings, a Ukrainian gas company at the center of a scandal. He was a member of the board while his father was vice president. This was why President Trump wanted the Ukrainian government to investigate the Bidens in the fateful phone call that ultimately resulted in his impeachment by the House of Representatives.

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Hawley added that jurors should hear from the whistleblower as well because “that is somebody who is directly relevant here.” Hawley acknowledged that he doesn’t know the identity of the whistleblower and said that should be revealed.

“We are in an impeachment trial now. This is about overturning an election by the people of the United States and if we're going to call witnesses, the whistleblower needs to be put under oath and explain what he knew and when he knew it,” Hawley said on Monday.

He also reacted to a report in The New York Times revealing a bombshell excerpt from Bolton’s forthcoming book that could prove pivotal in Trump’s impeachment trial.

The Times exclusively reported on Sunday that Bolton's manuscript included a claim that Trump explicitly linked a hold on Ukraine aid to an investigation of Joe and Hunter Biden. Trump told Bolton in August, according to a transcript of Bolton's forthcoming book reviewed by the Times, "that he wanted to continue freezing $391 million in security assistance to Ukraine until officials there helped with investigations into Democrats including the Bidens."

Trump refuted Bolton's claims on Twitter on Sunday.

“I can't tell from The New York Times report what is actually being reported here,” Hawley said.

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“I can't tell if this is something new. I can't tell if they have actually seen the manuscript. It's all a bunch of hearsay, and clearly it’s an attempt to try to influence the course of the trial.”

Fox News’ Gregg Re and Gillian Turner contributed to this report.