AT&T's WarnerMedia said on Tuesday that its HBO Max streaming service will launch in the U.S. in May of 2020, and cost $14.99 a month.

At a company event in Burbank, California, WarnerMedia CEO John Stankey said that content, technology platform and marketing and distribution are the "three pillars" for a successful streaming service. He said AT&T is best positioned for all three.

"We're all in," said Stankey.

HBO Max is one of the newest additions to an extremely crowded streaming market that will soon include Disney+ and Comcast's Peacock. They're all taking aim at Netflix, Amazon, Hulu and Apple, which have a variety of subscription and ad-based offerings.

HBO Max will start with about 10,000 hours of content, including movies, original content and classic TV shows. That's "less than some of our competitors," said Bob Greenblatt, chairman of WarnerMedia Entertainment, at the event.

The company said it will spend $4 billion over the next three years building HBO Max. It expects annual incremental revenue, from subscriptions, content and ads, to hit $5 billion by 2025, which is the year it should start to positively impact earnings.

There will be 50 HBO Max originals in 2021. The Batman spinoff film "Joker" will be available at launch, a highlight of WarnerMedia's DC Comics library, which includes both movies and TV shows. The service will have 23 seasons of the animated comedy "South Park," with three new seasons to come. They will debut on HBO Max a day after they're available on Comedy Central.

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HBO will launch an advertisement-based HBO Max offering in 2021, less than a year after the ad-free version hits the market. The goal is to reach 75 to 90 million subscribers by 2025, Stankey said.

Disclosure: Comcast owns NBCUniversal, the parent company of CNBC.

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