Former South Carolina Rep. Trey Gowdy suggested that Barack Obama and Joe Biden could be important witnesses in the Senate impeachment trial of President Trump.

"Part of impeachment is setting a precedent for what's going to happen in the future," Gowdy told Fox News.

"So, if the vice president can make that assertion, then he is relevant as a witness, but so, too, is President Obama, because I would want to know whether or not he had the authority of the president at the time he made that pronouncement that there will be no loan guarantees unless the prosecutor is fired," he added.

Biden bragged in 2018 about strong-arming Ukraine into firing a prosecutor by threatening to renege on a loan guarantee.

"I was supposed to announce that there was another billion-dollar loan guarantee, and I had gotten a commitment from Poroshenko and from Yatsenyuk that they would take action against the state prosecutor. And they didn’t," Biden said during an appearance at the Council on Foreign Relations.

"I said, 'Nah, I’m not going to — or, we’re not going to give you the billion dollars,'" he added.

The former vice president then told an audience that he called Obama and the prosecutor was fired.

Gowdy explained to Sean Hannity that "if President Obama gave Joe Biden permission to condition loan guarantees on the firing of a prosecutor, then that makes both of them potentially relevant as witnesses."