Two snack companies are giving new meaning to the term "bar fight."

Clif Bar's co-CEOs Gary Erickson and Kit Crawford have challenged energy bar maker Kind Snacks to "do a truly kind thing" and use organic ingredients, publishing an open letter to Kind founder Daniel Lubetzky in a full-page ad in Wednesday's New York Times. In the letter, the co-CEOs offer their organic ingredient "expertise" to Kind, calling the offering "Open Source Organic." Clif Bar also pledged to donate 10 tons of organic ingredients to Kind if the company accepts the challenge. 

"We know how strange this offer sounds coming from a competitor," the ad reads. "But more than ever, we believe that making the world better means making it organic."

Clif Bar began using organic ingredients in 2003 and now reports that 76 percent of its ingredients are organic, though the company is still on a "relentless quest" to become 100 percent organic.

While the ad is a highly orchestrated public relations stunt, a Kind representative tells Inc. that it's not a joint marketing campaign. Indeed, Kind's response to the challenge suggests the company is not keen on using organic ingredients.

"Clif's approach in selling snacks made predominantly from organic brown rice syrup, which is basically sugar, isn't the solution," Kind CEO Lubetzky said in a statement shared with Inc. "We'd be happy to meet and share why Kind focuses on making snacks that always lead with nutrient-dense ingredients like whole nuts, whole grains & whole fruit--instead of sugar. That is why Kind's leading snack bars have a fraction of the sugar in Clif's line up."

Kind states on its website that it is not "currently pursuing organic certification" for its products, saying its top priority is investing in "high quality, premium ingredients." In the ad, Clif bar states that the benefits of going organic include having fewer synthetic fertilizers "polluting soil and water" and helping to fight climate change "by storing more carbon in the soil." The company also challenged nutrition bar companies RXBAR and LÄRABAR to go organic in the ad. 

Last September, Clif Bar was estimated to generate between $500 million and $1 billion in annual revenue. Forbes recently estimated that Kind generates $800 million in annual sales.

A Clif Bar spokesperson was not immediately available for comment.