President Trump is delivering a prime-time address on Thursday, but where the speech will air live on traditional television remains something of an open question.

Both Fox News and the Fox broadcast network will carry the president’s address live, according to Bret Baier, Fox’s chief political anchor.

But ABC, CNN and NBC are not planning to pre-empt regularly scheduled programming at 9 p.m. when Mr. Trump speaks. CBS and MS NOW did not respond to inquiries about their plans.

The uncertainty is a direct result of the potential for Mr. Trump’s speech to become partisan or incendiary. The president is expected to raise the specter of voter fraud in the 2020 presidential election, according to people familiar with his plans. Mr. Trump has said his address will concern election security, and that he has “really, really big news” to share.

If Mr. Trump makes unsubstantiated allegations of election rigging, network executives will need to decide whether to ask their anchors to break in and fact-check the president’s remarks, or wait until he is finished speaking to provide context.

NBC News said that it planned to broadcast a special report on Thursday after the president’s remarks; ABC said it was “fully prepared” to air a special report “should significant developments occur.”

Many of the networks — including ABC, CNN and NBC — said that they would carry Mr. Trump’s speech live on their digital streaming services.

Presidents do not have an automatic right to appear on prime-time television whenever they wish; former Presidents Barack Obama and Joseph R. Biden Jr. both had some requests denied. In the past, network executives have been loath to accommodate speeches that they view as distinctly political in nature, especially during election years.

Evening programming is usually the most lucrative time of day for TV networks, and in the absence of breaking news, White House aides typically approach producers days beforehand with their requests.

Some networks may also be grappling with legal concerns. Fox News paid $787 million to settle a defamation lawsuit stemming from false claims about election interference that appeared on its airwaves in 2020.

A spokesman for Newsmax, a right-wing cable channel, said the channel planned to carry Mr. Trump’s remarks.