By Alex Heath

AT&T is in talks to acquire the advertising company AppNexus, Cheddar has learned.

Privately-held AppNexus operates one of the largest independent ad exchanges, which facilitates the buying and selling of digital ads. The purchase by AT&T would signal the telecom giant’s ambition to challenge the dominance of Google and Facebook in online advertising.

People familiar with the talks told Cheddar that the deal is close to being finalized. The price of the planned transaction couldn’t be learned, but one person close to AppNexus said the company would likely not sell for less than $2 billion.

AT&T and AppNexus both declined to comment for this article.

AT&T recently won court approval to buy Time Warner for $85 billion, a landmark acquisition that gives the company ownership of Turner, HBO, and the Warner Bros. film studio. After the Time Warner (now WarnerMedia) deal was approved last week, AT&T CEO Randall Stephenson told CNBC that the company was also in the process of starting a “significant advertising platform” and would announce at least one other acquisition “in the coming weeks to demonstrate our commitment to that.”

Leading AT&T’s efforts to build an advertising business is Brian Lesser, the former CEO of GroupM North America who joined AT&T in October 2017. Lesser previously sat on the board of AppNexus. AT&T is already one of AppNexus’s biggest customers, according to a person familiar with the business.

AppNexus originally planned to hold an initial public offering in early 2017 but backed out of the process, according to another person close to the company. CEO Brian O’Kelly told Cheddar a few months ago that the business was “very, very financially healthy.” The New York-based company has raised roughly $344 million in private funding since it was founded in 2007.

Buying AppNexus would give AT&T the kind of scaled ad buying and analytics platform needed to monetize its newly-purchased content from WarnerMedia, BTIG media analyst Rich Greenfield told Cheddar on Tuesday.

“It's virtually impossible to compete with the scale of Google and Facebook today,” he said. “Buying AppNexus gets the buyer in the game with a scaled, global, open platform that could be uniquely valuable to a buyer who is trying to improve monetization across mobile devices.”

Stephenson recently said that AT&T planned to launch an ad-supported streaming video service that will include content from WarnerMedia properties like Turner, which owns CNN, TBS, TNT, and other TV channels.