Comcast Corp.’s NBCUniversal said its upcoming streaming service will be free to everyone -- with extra programming for its pay-TV subscribers -- in a bet that it can generate substantial revenue from advertising while supporting the cable business.

Along with AT&T Inc.’s HBO Max, NBC’s new service, Peacock, stands to be a relatively late entrant in the burgeoning market for streaming-video services. But Peacock also marks a very different approach from other new streaming services. Unlike paid-subscription rivals such as Netflix Inc., Walt Disney Co.’s Disney+ and Apple Inc.’s Apple TV+, Peacock will largely rely on advertising. The company expects to reach 30 million to 35 million active accounts by 2024.

Comcast executives have said they plan to spend $2 billion over the next two years on the streaming service and expect it to break even by its fifth year.

The service will launch April 15 to Comcast customers and then roll out nationwide July 15, just before the start of the Summer Olympics, which NBCUniversal’s networks will air. The premium version of Peacock, which ordinarily will cost $4.99 a month, will be available at no cost initially to subscribers of Comcast and Cox Communications Inc.

Those two cable companies have over 24 million subscribers. Their subscribers will have access to twice as many hours of content as those using the free version. That will include sports offerings like soccer’s English Premier League and early access to late-night talk shows.