(Bloomberg) -- Mercedes-Benz, attempting to grab an edge in the race to topple Lexus, has enlisted tennis star Serena Williams and a tweeting mom from suburban Chicago to add online buzz to its first advertising appearance during the Super Bowl telecast.

BMW AG and Volkswagen AG's Audi will also air ads during the Feb. 6 broadcast of the American football championship, marking the first time all three German luxury brands are advertising at the biggest U.S. television event. At last year's game, advertisers paid $3 million for a 30-second slot, according to The Nielsen Co.

“The Germans are seeing Lexus as vulnerable, so they're pulling out all the stops,” said Bill Visnic, an analyst at U.S. auto website Edmunds.com. The failure to beat Toyota Motor Corp.'s Lexus has been “a burr under the saddle” of the German automakers in the 11 years since Lexus snatched the top spot.

BMW, Daimler AG's Mercedes unit and Audi, the top-three luxury brands, dominate sales everywhere except the U.S., where Lexus gained popularity with its sport-utility vehicles and hybrids. The Super Bowl campaigns underscore their growth ambitions in the world's biggest luxury-car market, as Lexus seeks to shake off the effects of Toyota's recalls last year.

Close race

Lexus sold 229,329 vehicles in the U.S. in 2010, compared with BMW's 220,113 and Mercedes 216,448. Audi delivered 101,629 cars and SUVs in the country in the 2010, the first time its U.S. sales topped 100,000. Globally, all three German carmakers each sell more than 1 million cars annually, compared with about 400,000 at Lexus.

Aside from television commercials, Mercedes is spending $290 million on its factory in Alabama and will assemble the C-Class sedan there beginning in 2014. BMW completed a $750 million expansion of its South Carolina plant late last year, while Audi has vowed to double U.S. sales to 200,000 by 2018.

Lexus won't follow its German rivals to the Super Bowl, which will be held near Dallas this year. The Toyota unit, which saw its U.S. lead over BMW shrink by more than half in 2010, won't air any spots or sponsor game-related events, said Allison Takahashi, a Lexus spokeswoman in Torrance, Calif.

The 2010 game, won by the New Orleans Saints, was watched by 106.5 million people, making it the most popular American TV program ever, according to TV audience rater Nielsen. The popularity of the broadcast, which is watched as much for the commercials as the sports, makes it a sought-after platform.

‘Getting bolder'

“This is us stepping up on the biggest stage and saying we belong there,” said Steve Cannon, vice president of marketing for Mercedes' U.S. unit. “We're getting bolder.”

The intensity of the competition is evident in a new Audi ad, which features a Mercedes S-Class. In the 60-second spot, which began airing Jan. 13 as a run-up to Audi's fourth straight Super Bowl campaign, the lights in the Mercedes sedan turn off as the narrator says, “Goodnight old luxury.” The ad then promotes Audi's A8 flagship as the face of “new” luxury.

The marketing battle could spill over into better deals as manufacturers vie for market share even with many buyers still scarred by the recession.

“When you look at Audi's ambitions and the size of the Toyota war chest backing Lexus, it seems that you'll see increased incentives,” said Edmunds.com's Visnic. “It's still a little bit not cool to park a big new BMW in your driveway. They still have to tease buyers out of their bunkers.”

Facebook contest

BMW bought two 30-second spots and will advertise during the Super Bowl for the first time in 10 years, Jim O'Donnell, head of BMW's U.S. unit, told reporters at the Detroit auto show.

The Munich-based company on Jan. 21 started a Facebook contest around its Super Bowl commercial featuring the revamped X3 SUV, which is built in South Carolina. Contestants try to guess the configuration of the car to be featured to win a two-year lease and a trip to the factory.

Mercedes will push a younger, hipper image by focusing on sporty new models. The spot will feature a roadster version of the $185,750 SLS supercar, the new C-Class coupe as well as the revamped CLS luxury four-door coupe and SLK hard-top roadster, spokeswoman Donna Boland said.

In addition to the spots, Mercedes is sponsoring a tweet race in which teams driving specially-equipped vehicles need to generate traffic on Twitter to win a C-Class coupe. The four two-person teams will have to generate about 10 tweets per mile, or about 15,000 tweets, to reach Cowboys Stadium from respective starting points in Chicago, Los Angeles, New York, and Tampa. The teams also must complete tasks on the way.

Rev Run, Nick Swisher

“That's a crap load,” said Todd Sanders, a tweeting ice fisherman and Green Bay Packers fan whose team will drive an S- Class with front seats equipped with four-stage massage.

“The last thing you want to do is spam your followers,” said Sanders, 37, a web manager for the University of Wisconsin- Green Bay. “It's going to be tricky.”

The three-day race, which starts Feb. 2, features hip hop artist Rev Run from the group Run-D.M.C., tennis star Serena Williams, rock musician Pete Wentz and New York Yankees baseball player Nick Swisher as coaches to drum up traffic. The celebrities each have more than 1 million Twitter followers.

The tweet race marks an “aggressive” play by Mercedes for consumers under 40, said Ian Beavis, a Los Angeles-based Nielsen consultant. The average U.S. Mercedes customer is 54, according to San Diego-based researcher Strategic Vision.

“We're pushing perceptions of the brand,” Mercedes executive Cannon said earlier this month in Detroit. “We're captivating the imagination of younger drivers.”

Tweeting race

While there's a risk Mercedes loses control of the promotion to Twitter users, the costs are relatively low and the automaker has the opportunity to gain a following it can tap into again, said Nielsen's Beavis, who advises auto companies on brand and media strategy.

“This is a total leap of faith,” said Jennifer Marshall, the Chicago-area mother of seven-year-old twins who tweets and blogs under the tag nuckingfutsmama. “I was totally in shock when I heard we were going.”

Marshall, 38, turned to Twitter as “a way of getting that instant feedback that a stay-at-home mom doesn't get,” she said. She and teammate Meredith Sinclair, fellow mom tweeter known as Hoo-Dee-Hoo, will drive a diesel-powered GL SUV to the game, while their husbands watch the kids.

“They're a little jealous,” she said.