The head of President Trump’s re-election campaign accused CNN of “censorship” on Tuesday afternoon after the broadcast network refused to run the group’s latest advertisement.

CNN said it would run the 30-second television spot, a celebration of Mr. Trump’s first 100 days in office, only if the campaign removed a section that featured the words “fake news” superimposed over several TV journalists, including Wolf Blitzer of CNN, and others from MSNBC, PBS, ABC and CBS.

CNN defended the decision in a statement on Twitter.

“The mainstream media is not fake news, and therefore the ad is false,” the network said. “Per our policy, it will be accepted only if that graphic is deleted.”

In response, Michael Glassner, the executive director of Mr. Trump’s campaign committee, called the decision “censorship pure and simple.”