Former Vice President Joe Biden is pressuring Fox News not to run an ad sponsored by President Donald Trump’s 2020 election campaign.

CNN has already refused to air the spot that suggests Biden exercised political influence in Ukraine on behalf of his son, Hunter Biden. The network also claimed the ad mocked its evening news host Chris Cuomo.

The Biden campaign would like Fox to do likewise, and it asserted Thursday that the ad “spreads false, definitively debunked conspiracy theories,” Politico reported. (RELATED: Nunes: Ukraine Will Sink Biden’s Campaign, Not Trump’s Presidency)

In a letter to Fox News and Fox Business general counsel Lily Claffee, Biden campaign manager Greg Schultz claims that the ad “falsely states” that “Biden offered Ukraine $1 billion to fire the prosecutor investigating a company affiliated with his son,” according to Politico.(RELATED: Joe Biden Says He Never Discussed Hunter Biden’s Ukraine Deal. Hunter Says He Did)

“Though the Trump campaign is prepared to fabricate outright lies, your station’s airwaves should not be used to disseminate them,” Schultz wrote, per Politico. “We are putting you on notice about the absolute falsity of the advertisement’s claims, and we expect that you will reject it. Please consider this letter a standing request that you reject any advertisement containing similar claims, regardless whether the Trump campaign or a third-party group seeks to place it.”

But Fox isn’t buckling to the Biden campaign’s warnings.

“We are not in the business of censoring ads from candidates on either side of the aisle,” a Fox News spokesperson told Politico. “Vice President Joe Biden has a standing invitation to appear on any of our platforms.”

In a statement to Politico, CNN reiterated its objection to the ad, writing, “CNN is rejecting the ad, as it does not meet our advertising standards. Specifically, in addition to disparaging CNN and its journalists, the ad makes assertions that have been proven demonstrably false by various news outlets, including CNN.”