MEXICO CITY (AP) – Boosters of Mexico’s traditional fast foods are battling McDonald’s, Burger King, Pizza Hut, KFC and other foreign chains that have taken a bite out of sales of tortillas, tacos and tortas.

With the celebration of the first national Torta Festival in Mexico City on Friday, they hope to promote this overstuffed sandwich of crusty bread, beans and cheese. By showcasing the torta – in part by building a 75-foot-long version – they are also trying to encourage its makers to modernize and diversify.

“Mexicans will never stop eating tortas. It’s our vitamin T,” said Maria Isabel Vazquez, a 47-year-old government worker visiting the festival.

Mexicans are famous for eating on the run, often grabbing tacos or quesadillas at crowded stands set up along everything from highways to sleepy side streets. But the increasing popularity of American favorites like hamburgers and hot dogs, as well as fast food chains like Subway and Domino’s, have hurt sales of the national cuisine.

“The torta is not in danger of extinction, but its sales have declined by 50 percent over the last decade because of the competition from pizza and hamburgers,” said Francisco Juarez, head of the Mexican National Restaurant Chamber’s Mexico City chapter.

On display at Friday’s festival are new designs and financing sources for torta stand owners, who slap avocado, tomato, chili and bean paste, together with meat and cheese, onto crusty bread rolls.

Oddly, the alarm about the torta’s future comes as Mexican favorites are making inroads in the United States. Consumption of tortillas is up in the United States, but down in Mexico.

Between 1998 and 2004, tortilla consumption in Mexico fell by 25 percent, from an average 308 pounds per person per year to 228 pounds, according to the National Corn Processors Chamber.

“Often, people will consume oriental-style noodles rather than a tortilla soup, because it’s quicker and easier to prepare,” said Jose Enrique Tron, director of the corn chamber.

Greater choice and prosperity are also to blame for the slide of tortillas, viewed as the food of the poor because they cost as little as 25 cents per pound.

“Maybe housewives are consuming products other than tortillas because they can afford to now, whereas before perhaps they couldn’t,” Tron said.

It’s not that Mexicans have lost their taste for tortillas or tortas. U.S.-style amusement parks that have opened in Mexico over the last decade prominently advertise “national food” to attract those who dislike hamburgers or hot dogs.

And the government plans to ask UNESCO in September to declare Mexican food a “cultural patrimony of humanity.”

The torta remains the king of sandwiches here, with an estimated 2,000 stands, stalls and holes-in-the-wall in Mexico City alone.

It’s just that torta makers feel out-marketed and outmaneuvered.

“Sales are way down, simply because of the multinationals, the pizza chains, the hot-dog chains,” said Jaime Martinez, 80, owner of Tortas Armando. “These companies have a lot of money, they can advertise. It’s hard to compete.”

The French introduced the torta’s bread rolls when they invaded Mexico in the 1860s.

Martinez said his great-aunt, Soledad Centurion, opened the first torta outlet in Mexico in 1892. He recalled that customers used to eat two or three tortas a day in the 1950s, when the sandwiches were smaller, snack items.

But starting in the 1980s, American chains arrived and quickly expanded. McDonald’s had one store in Mexico in 1985 – and 292 in 2004. Burger King has grown from one store in 1991 to 198 today. Pizza Hut, KFC and others also came, and they spawned Mexican imitators who magnified their effect.

But even Hipocampo says its sales have held steady instead of expanding by 10 percent as expected.

Tortilla makers, meanwhile, are experimenting with lighter, less caloric versions, as well as vitamin-enriched ones, blue-corn tortillas and wheat tortillas flavored with spices and vegetables.

It may all be an uphill battle, given the marketing power of the big chains.

“A lot of kids like Happy Meals, not so much for the hamburger, but for the toy,” Juarez said. “And it would be hard to imagine torta stands building play areas for the kids.”