Comcast, one of America’s largest media and communications companies, is wading into the epic regulatory pile-on against big tech companies such as Google, according to people familiar with the matter.

Behind the closed doors of a congressional task force last month, Comcast’s video ads division FreeWheel accused Alphabet’s Google of using privacy concerns as a pretext to limit FreeWheel’s ability to sell ads on behalf of its clients’ YouTube channels, four people briefed on the discussion said.

Comcast may be drawing a line in the sand and wants to avoid letting Google do to the video ad business what it has done to the online ad market.

It is the first time one of the most powerful companies in the United States, with its own muscular lobbying apparatus in Washington, is taking sides in the antitrust battle looming over the world’s largest seller of online ads. Google’s competitors are warning lawmakers that emerging privacy regulations could help Google extend its dominance.

“FreeWheel would embrace a solution that allowed it to continue to meaningfully serve its clients when they publish their content on YouTube, as it had for over a decade on that platform,” Comcast said in a statement. “Unfortunately, the actions to remove or degrade FreeWheel’s capabilities on YouTube fall well short of that.”