Wendy's is embroiled in a battle over fresh beef patties after the fast food chain came after on Twitter.

McDonald's announced in a tweet that it would use fresh beef in its Quarter Pounder burgers in most of its restaurants by mid-2018. Wendy's tweeted in response: "So you'll still use frozen beef in MOST of your burgers in ALL of your restaurants? Asking for a friend."

@Wendys Tweet: So you'll still use frozen beef in MOST of your burgers in ALL of your restaurants? Asking for a friend."

McDonald's has so far not yet responded to the tweet from Wendy's.

Wendy's CEO Todd Penegor said Monday that the fast food chain is being a "challenger with charm" and is simply defending its territory.

"If you think about our brand, right, we have been created on fresh never frozen North American beef since 1969," Penegor said on CNBC's "Power Lunch." "We have been serving fresh beef in all of our restaurants in all of our hamburgers for almost 48 years."

Credit Suisse analysts Jason West and Jordy Winslow said the push by McDonald's into the fresh beef territory could improve the company's same-store sales. They said 15 percent of those gains could be snatched from Wendy's, thus hurting the fast food chain's same-store sales by 30 basis points.

Penegor said he is not worried. He said he sees his rival's announcement as a chance to allow more customers to recognize them as the originals in the fresh beef patty space.

"Today about 3 in 10 consumers really understand that Wendy's is fresh never frozen," Penegor said. "We have a great opportunity to amplify that message."