CNN recently unveiled the slogan “go there,” but some ad-buying executives may not want to follow that command.

As CNN begins to hold upfront conversations, several ad buyers say the Time Warner-owned cable-news outlet is meeting with resistance. These buyers said CNN has historically been able to command high rates in the cost of reaching 1,000 viewers, a measure also known as a CPM that is central to the annual upfront market, when U.S. networks try to sell the bulk of their ad inventory for the coming season. In 2014, buyers say they are pushing back against the network’s initial terms.

Skepticism from buyers – a natural element of this yearly haggle – comes after CNN has reworked its positioning . The network, part of Time Warner’’s Turner unit, is relying more heavily in primetime on documentary series and during the rest of the day seeking out stories that help it stand apart from competitors, as it did when it followed the mysterious disappearance of Malaysia Airlines Flight 370.

Doing so, however, has CNN veering slightly from the pitch it has long thrown to Madison Avenue: For years, CNN has portrayed itself as a high-quality source of straight news, one that ought to command a premium. And the network still inhabits that role. But with its ratings slipping over the long term, and a new emphasis being placed on what buyers view as “entertainment programming” for an hour of primetime, sponsors are pushing for a reworking of the relationship CNN has had with advertisers.

“I’m pretty confident they’ll have to make some adjustments in the market this year,” said one media-buying executive.

The seeming standoff comes as CNN has been under more scrutiny in the past year. While CNN remains a go-to venue when big breaking news takes place, the network has found keeping viewers riveted to its screen a tougher task as competing news outlets have staked out new turf. Fox News Channel regularly wins more viewers than CNN. MSNBC provides competition as well. In the past year, new entrants have tested the waters. Al Jazeera America, while not generating big viewership, has bountiful cash reserves and a hard-news focus. Fusion, a new network backed by ABC and Univision, is experimenting with ways to reach Hispanic and millennial viewers.

Given an expanding field of players, it’s little wonder ad buyers want to try to carve out more favorable terms with CNN. News audiences can be purchased more efficiently elsewhere, several buyers suggested, especially in digital-only venues, which have attracted more consumers seeking information about current events.

CNN has been making its case to potential sponsors. In a presentation made in April, the network unveiled nonfiction series featuring personalities like Mike Rowe, Lisa Ling and John Walsh. Some of its documentaries like “The Sixties” and “Blackfish” have made a splash in popular culture and generated good ratings in the demographic coveted by advertisers in news programming, people between the ages of 25 and 54. In the case of “Blackfish,” the audience had one of the youngest median ages (40 years old) for a CNN primetime show in a decade, according to Nielsen.

And the network has been vocal about its efforts to move more breaking-news content to digital, mobile and social realms. In April, the network unveiled technology it called CNNx that will allow subscribers to watch 24 hours’ worth of news segments on demand via iPad and set-top box.

Ad buyers have chosen to focus on the price of reaching a CNN viewer. “Turner has sought a very high CPM, and the ratings are off” over the long term, said another ad-buying executive.

Turner is seeking CPM increases in line with the top of the market. NBC has held out for increases of 7% to 8% in the current market, according to people familiar with the situation.

CNN captured nearly $320 million in ad revenue in 2013, according to data from SNL Kagan, compared with $327.7 million in 2012 and $347.8 million in 2011.