A Fox News chyron appeared to refer to President Biden as a “wannabe dictator” during footage of his remarks from the White House on Tuesday, the same day that former President Donald J. Trump was charged with federal crimes in a Miami courtroom.

The onscreen text appeared briefly at the bottom of a split-screen broadcast that showed President Biden and Mr. Trump speaking from respective lecterns, at the White House and a Trump golf club in Bedminster, N.J.

“Wannabe dictator speaks at the White House after having his political rival arrested,” the chyron read. It did not refer to Mr. Biden by name, but the implication was clear.

The alert appeared at the end of the 8 p.m. broadcast of “Fox News Tonight,” a show that recently replaced one that had been hosted by Tucker Carlson, a popular prime-time host who was dismissed by the network in April. The footage of Mr. Biden showed him speaking on the South Lawn of the White House on Tuesday at a holiday event.

The term “wannabe dictator” was unusually strong even for a network that generally had a friendly relationship with the Trump White House and has been heavily critical of the Biden administration.

On Tuesday’s edition of “Fox News Tonight,” the host Brian Kilmeade also referred incorrectly to Mr. Trump as the “president of the United States” before Mr. Trump began speaking at his New Jersey club.

A spokeswoman for Fox News said, “The chyron was taken down immediately and was addressed.” She added that Mr. Kilmeade’s comment was an unintentional mistake.

Mr. Trump, the front-runner for the 2024 Republican presidential nomination, on Tuesday became the first former president to be charged with federal crimes. He pleaded not guilty to 37 counts related to his handling of classified documents after he left office and his refusal to return them.

Later on Tuesday, after Mr. Biden delivered remarks during a White House reception for American diplomats, he declined to answer questions from reporters in the room about Mr. Trump’s courtroom appearance.

A number of major television networks have declined to broadcast Mr. Trump’s speeches live out of concern that doing so could give him a platform for spreading misinformation. When CNN hosted a town hall with Mr. Trump in May, it was roundly criticized by observers who called the decision to air the event live irresponsible.

Since the 2020 election, Fox News has occasionally cut away from Mr. Trump’s speeches or declined to run them. In other cases, as on Tuesday, the network has given them prime-time slots.