Taco Bell is going to start thinking outside "Think outside the bun."

The chain is well known for its current tagline, as well as its previous "Yo quiero Taco Bell" and "Run for the border." But the taco giant is introducing a new slogan, "Live mas" ("mas" is Spanish for "more"), as it tries to reverse its sales misfortunes.

According to a Taco Bell spokesman, the new line underscore the brand's "commitment to value, quality, relevance and an exceptional experience." It signifies a move from the idea of "food as fuel" to food as experience and lifestyle.

On Feb. 25, Taco Bell, which is celebrating its 50th anniversary this year, will roll out a campaign featuring the slogan with TV spots airing on TNT's NBA All-Star Saturday Night and then nationally. The campaign was developed by Taco Bell's agency, Interpublic's DraftFCB. The agency did not comment and referred calls to the client.

The chain spent about $250 million on U.S. measured media in 2011, according to Kantar. It is clearly banking on overhauls in its marketing and menu to turn its sales performance around. A national product launch -- for Doritos Locos Taco, a taco with a Doritos shell -- on March 8 is aimed at bringing in major traffic. Taco Bell CEO Greg Creed calls it the chain's biggest product launch ever. (Doritos is owned by PepsiCo, with which Taco Bell has a contract for beverages.)

It also introduced breakfast in nearly 800 locations in January. The rollout included a cobranded menu with brands such as Johnsonville, Cinnabon and Tropicana. And it's testing what it calls the Cantina menu, which is more upscale and focused on fresh ingredients (like Chipotle but at a lower price point).

While a different tagline may get some attention, will it be enough to spur a turnaround?

"It's not going to be a slogan but the desirability of the food that carries them," said Dennis Lombardi, executive VP-foodservice strategies at WD Partners. "The slogan will build awareness about the food and initiate possible trial. But they're going to need more than trial to substantially increase their sales -- and that means frequency."

Some argue that Live Mas might be a stretch for the brand.

"They're trying to suggest a lifestyle aspiration, but this seems an overreach for Taco Bell, as is their Cantina Bell menu effort," said Denise Lee Yohn, a restaurant-marketing consultant. "A tagline should embrace the DNA of the brand, which for Taco Bell is extraordinary value," she said, adding that value messaging would resonate in this economy.

Ms. Lee Yohn also suggested that using "imperative taglines" seems outdated and that Taco Bell should use a tagline that communicates the brand's personality, spirit, or values, such as Chipotle's "food with integrity."

The new campaign comes nearly 10 months after Taco Bell's franchisee council pressed the chain for an agency review. In a letter, the council expressed discontent with the chain's handling of a lawsuit concerning its ingredients as well as with its "value messaging." If Taco Bell launched a review, the letter said, "without a doubt, we will learn new things, obtain fresh ideas, and be further ahead, even if we decide to stay with the incumbent agency."

Four months ago, Taco Bell hired marketing chief Brian Niccol, a former CMO at Pizza Hut.

Taco Bell's parent company, Yum Brands, has been experiencing strong growth overseas, particularly in China. But the company, which also owns Pizza Hut and KFC, has been struggling in the U.S.

Yum 's same-store sales fell 1% in 2011. That included full-year declines of 2% at both KFC and Taco Bell, its most profitable brand in the U.S.; Pizza Hut's sales were flat last year. Fourth-quarter same-store sales rose 1%, driven by 6% growth at Pizza Hut but offset by drops of 2% at Taco Bell and 1% at KFC.

Taco Bell has blamed its 2011 sales problems on a false-advertising lawsuit related to its ground beef. Bernstein Research analyst Sara Senatore said in a recent report that the damage to Taco Bell's reputation had largely faded, and "given that Taco Bell comps have been positive through [first-quarter 2012], we expect new product launches (e.g., Doritos Locos Tacos in mid-March) and day parts (e.g., breakfast) to help sustain the trend."