SAN FRANCISCO/NEW YORK (Reuters) - Three years ago, the beginning of the end of the U.S. television business looked certain when one of the largest ad buying agencies vowed to move a big chunk of its purchases to YouTube from TV budgets.

FILE PHOTO: Silhouettes of mobile device users are seen next to a screen projection of Youtube logo in this picture illustration taken March 28, 2018. REUTERS/Dado Ruvic/Illustration

The TV business did not die; far from it. Instead, data compiled by ad tracking firm MediaRadar at Reuters’ request shows some advertisers are spending more on television networks’ online properties and less on Alphabet Inc’s video service. The data may partially explain why Google’s parent had its slowest quarterly revenue growth in three years.

This week, the big U.S. TV networks plan to drive the knife further into digital rivals, repeating the phrase “brand safety” and exploiting YouTube’s struggle to curb unsuitable content, during the upfront ad sales period when TV networks preview the fall season for advertisers.

On stage and in private meetings, executives from Comcast Corp’s NBCUniversal, CBS Corp and Viacom Inc say they are pitching themselves as one-stop shops because they have viewers on TV, their own streaming services and YouTube.

“Across every screen, clients can rest easy knowing that their message is in a pristine, premium environment. And that’s something other platforms just can’t guarantee,” said Trevor Fellows, executive vice president of digital sales and strategy for NBCUniversal.

Out of a sample of 240 companies that advertised on YouTube during last year’s first quarter and on TV networks’ online services in this year’s first quarter, 46 percent spent less on YouTube than a year ago and more on networks’ online properties, according to MediaRadar. These companies include major U.S. advertisers Pfizer Inc, Verizon Communications Inc and Adidas.

Only 8 percent of advertisers spent more on YouTube and less on the network properties, MediaRadar found.

Pfizer, Adidas and Verizon declined comment on their ad spending. YouTube declined to comment for this article, but said this month in its presentation to advertisers that its growing audience is unrivaled by TV.

‘EMPIRE’ STRIKES BACK

YouTube’s struggle to clean up content has driven advertisers to networks including CBS and Viacom, according to people involved in the ad businesses at each of the companies speaking on the condition of anonymity.

One example is “Carpool Karaoke,” a segment from “The Late Show with James Corden” on CBS which has performed well on YouTube, said one CBS executive.

CBS can sell YouTube ads during its clips on YouTube, and ensure a brand-safe environment, the executive said.

YouTube keeps about 45 percent of ad revenue from user videos, but generally takes a lower cut from content uploaded by TV networks.

An executive at a major ad buying agency said networks this year are touting their strength in high quality content across multiple screens, a significant departure from trying to compete with YouTube and Facebook by talking about tech.

“It’s like return of the empire in some ways,” the buyer said.

A second major U.S. ad buying firm said its annual spending on YouTube will grow at a slower rate for the first time this year.

The networks have made strides online in allowing advertisers to direct ads to certain demographics, according to network sources. CBS is able to match advertisers with viewers based on their reading history at its CNET tech news website, the executive said.

But the big selling point for networks is the bulk of TV programming is vetted for decorum standards.

YouTube screens all videos available for advertising in Google Preferred, a popular batch of content set aside for advertisers making big spending commitments.

The selection represents a only fraction of advertising opportunities on YouTube. Still, that fraction appears to be growing according to YouTube data showing users spent 30 percent more time watching Google Preferred videos during last year’s fourth quarter than a year earlier.

This month, YouTube announced Google Preferred content also must have high production quality and be frequently watched on a TV, making its package more comparable to TV networks’ offerings.