Billions of YouTube videos — from free amateur pet tricks to movie trailers — will be available on televisions through Comcast, the cable giant said Monday.

Comcast, the nation's largest cable-TV and residential internet provider, will integrate the Google-owned video streamer into its X1 set-top box later this year, blurring the line between traditional pay-TV and the internet.

To gain access to YouTube, a Comcast subscriber will have to order bundled Comcast TV and internet, thus paying for both services. The move could also help forestall another effort to reform set-top box rules in Washington.

The new YouTube offering shows that Comcast -- which has x1 boxes in about half of its TV subscriber homes -- doesn't view free streaming services as the dire threat to its pay-TV model as it once did.

It also appeases search-engine giant Google. The California firm, which had close ties to the Obama administration, lobbied the Federal Communications Commission for set-top reforms for several years.

Thomas Wheeler, the FCC's former chairman, said in 2016 that new on-demand streaming services such as Google and Netflix should be as available on televisions as traditional pay-TV entertainment as part of the set-top box reforms.

Wheeler ran out of time to formally implement those reforms when he resigned from the agency last month, though Comcast had moved quickly to placate him by adding Netflix to X1 in late 2016 , and now has followed up with YouTube.

"We are excited to partner with Google to bring YouTube to X1 and provide our customers with easier access to all the content they love in one place," said Sam Schwartz, Comcast Cable's chief business development officer, in a statement.

Comcast chief executive Brian Roberts was expected to talk about adding YouTube at an investor conference on the West Coast late Monday.

YouTube will be free to Comcast subscribers with the X1 set-top boxes but they will have to subscribe to both Xfinity TV and Xfinity Internet. Meanwhile, the data consumed watching YouTube on X1 will count toward an Xfinity Internet subscriber's data stream that could lead to extra charges if an individual exceeds one terabyte of consumed data in a month.

The one-terabyte data caps have been instituted in about 70 percent of Comcast's cable-TV areas but not in the northeastern United States. Fewer than 1 percent of Comcast Xfinity Internet users exceed the one terabyte of data, which allow an individual to stream 600 to 700 hours of high-definition video in a month, Comcast says.

John Bergmayer, senior counsel to the nonprofit advocacy group Public Knowledge, said Monday that "Google is seen less an existential threat [to Comcast] and more as a business partner. So why not do business with them?"

The Comcast model, he said, "is to very slowly improve their service and then tell people, 'see, we are improving what we give you.'" That way, he said, Comcast can say it doesn't need more regulations.

Matt Wood, policy director with the nonprofit Free Press, said that Comcast's main goal is to keep people on its network and "get them to pay twice" -- for the TV and the internet.

Like other entertainment on X1, YouTube videos will be accessible through the X1 voice-controlled remote control so that Xfinity TV customers can talk to the remote to find the video once the YouTube app is launched.

A very popular aspect of YouTube is the streamed music videos.